Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.98	5.102%	$182.8565	$182.86	$182.85	$182.90
Purchase #2	$196.61	13.506%	$223.1641	$223.16	$223.15	$223.20
Purchase #3	$168.64	13.784%	$191.8853	$191.89	$191.90	$191.90
Purchase #4	$140.87	7.755%	$151.7945	$151.79	$151.80	$151.80
Purchase #5	$148.49	5.254%	$156.2917	$156.29	$156.30	$156.30
Purchase #6	$120.33	8.660%	$130.7506	$130.75	$130.75	$130.80
Purchase #7	$139.95	4.809%	$146.6802	$146.68	$146.70	$146.70
7 purchase totals =	$1,088.87		$1,183.4229	$1,183.42	$1,183.45	$1,183.60