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	$57.46	5.401%	$60.5634	$60.56	$60.55	$60.60
Purchase #2	$213.78	4.607%	$223.6288	$223.63	$223.65	$223.60
Purchase #3	$227.31	12.438%	$255.5828	$255.58	$255.60	$255.60
Purchase #4	$58.85	4.107%	$61.267	$61.27	$61.25	$61.30
Purchase #5	$242.88	8.327%	$263.1046	$263.10	$263.10	$263.10
Purchase #6	$57.65	8.392%	$62.488	$62.49	$62.50	$62.50
Purchase #7	$74.66	6.125%	$79.2329	$79.23	$79.25	$79.20
7 purchase totals =	$932.59		$1,005.8675	$1,005.86	$1,005.90	$1,005.90