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	$71.50	11.112%	$79.4451	$79.45	$79.45	$79.40
Purchase #2	$212.33	8.265%	$229.8791	$229.88	$229.90	$229.90
Purchase #3	$81.65	4.314%	$85.1724	$85.17	$85.15	$85.20
Purchase #4	$205.47	7.834%	$221.5665	$221.57	$221.55	$221.60
Purchase #5	$104.45	5.561%	$110.2585	$110.26	$110.25	$110.30
Purchase #6	$219.46	6.110%	$232.869	$232.87	$232.85	$232.90
Purchase #7	$39.40	8.153%	$42.6123	$42.61	$42.60	$42.60
7 purchase totals =	$934.26		$1,001.8029	$1,001.81	$1,001.75	$1,001.90