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	$159.30	5.734%	$168.4343	$168.43	$168.45	$168.40
Purchase #2	$215.78	10.685%	$238.8361	$238.84	$238.85	$238.80
Purchase #3	$79.27	8.150%	$85.7305	$85.73	$85.75	$85.70
Purchase #4	$184.45	6.774%	$196.9446	$196.94	$196.95	$196.90
Purchase #5	$214.65	6.855%	$229.3643	$229.36	$229.35	$229.40
Purchase #6	$160.74	5.528%	$169.6257	$169.63	$169.65	$169.60
Purchase #7	$65.75	5.506%	$69.3702	$69.37	$69.35	$69.40
7 purchase totals =	$1,079.94		$1,158.3057	$1,158.30	$1,158.35	$1,158.20