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	$228.64	13.335%	$259.1291	$259.13	$259.15	$259.10
Purchase #2	$61.63	7.627%	$66.3305	$66.33	$66.35	$66.30
Purchase #3	$156.54	7.739%	$168.6546	$168.65	$168.65	$168.70
Purchase #4	$177.36	7.793%	$191.1817	$191.18	$191.20	$191.20
Purchase #5	$249.29	13.362%	$282.6001	$282.60	$282.60	$282.60
Purchase #6	$177.26	4.302%	$184.8857	$184.89	$184.90	$184.90
Purchase #7	$148.82	13.380%	$168.7321	$168.73	$168.75	$168.70
7 purchase totals =	$1,199.54		$1,321.5138	$1,321.51	$1,321.60	$1,321.50