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	$59.42	7.792%	$64.05	$64.05	$64.05	$64.10
Purchase #2	$181.37	10.585%	$200.568	$200.57	$200.55	$200.60
Purchase #3	$102.78	10.244%	$113.3088	$113.31	$113.30	$113.30
Purchase #4	$196.76	10.241%	$216.9102	$216.91	$216.90	$216.90
Purchase #5	$141.65	10.365%	$156.332	$156.33	$156.35	$156.30
Purchase #6	$58.98	12.604%	$66.4138	$66.41	$66.40	$66.40
Purchase #7	$228.45	6.614%	$243.5597	$243.56	$243.55	$243.60
7 purchase totals =	$969.41		$1,061.1425	$1,061.14	$1,061.10	$1,061.20