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	$155.50	11.310%	$173.0871	$173.09	$173.10	$173.10
Purchase #2	$55.67	11.785%	$62.2307	$62.23	$62.25	$62.20
Purchase #3	$121.90	6.678%	$130.0405	$130.04	$130.05	$130.00
Purchase #4	$162.94	4.206%	$169.7933	$169.79	$169.80	$169.80
Purchase #5	$230.74	6.444%	$245.6089	$245.61	$245.60	$245.60
Purchase #6	$73.75	6.139%	$78.2775	$78.28	$78.30	$78.30
Purchase #7	$96.97	9.849%	$106.5206	$106.52	$106.50	$106.50
7 purchase totals =	$897.47		$965.5586	$965.56	$965.60	$965.50