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	$243.73	8.132%	$263.5501	$263.55	$263.55	$263.60
Purchase #2	$78.69	10.267%	$86.7691	$86.77	$86.75	$86.80
Purchase #3	$221.50	5.502%	$233.6869	$233.69	$233.70	$233.70
Purchase #4	$70.36	4.859%	$73.7788	$73.78	$73.80	$73.80
Purchase #5	$30.27	8.591%	$32.8705	$32.87	$32.85	$32.90
Purchase #6	$201.60	10.198%	$222.1592	$222.16	$222.15	$222.20
Purchase #7	$162.26	13.128%	$183.5615	$183.56	$183.55	$183.60
7 purchase totals =	$1,008.41		$1,096.3761	$1,096.38	$1,096.35	$1,096.60