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	$157.40	10.334%	$173.6657	$173.67	$173.65	$173.70
Purchase #2	$122.98	13.647%	$139.7631	$139.76	$139.75	$139.80
Purchase #3	$96.63	9.421%	$105.7335	$105.73	$105.75	$105.70
Purchase #4	$175.61	11.777%	$196.2916	$196.29	$196.30	$196.30
Purchase #5	$188.74	12.751%	$212.8062	$212.81	$212.80	$212.80
Purchase #6	$102.72	6.227%	$109.1164	$109.12	$109.10	$109.10
Purchase #7	$183.66	4.123%	$191.2323	$191.23	$191.25	$191.20
7 purchase totals =	$1,027.74		$1,128.6088	$1,128.61	$1,128.60	$1,128.60