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	$90.29	7.128%	$96.7259	$96.73	$96.75	$96.70
Purchase #2	$149.71	4.803%	$156.9006	$156.90	$156.90	$156.90
Purchase #3	$55.87	6.110%	$59.2837	$59.28	$59.30	$59.30
Purchase #4	$120.61	13.638%	$137.0588	$137.06	$137.05	$137.10
Purchase #5	$160.91	4.830%	$168.682	$168.68	$168.70	$168.70
Purchase #6	$229.90	6.819%	$245.5769	$245.58	$245.60	$245.60
Purchase #7	$60.95	6.453%	$64.8831	$64.88	$64.90	$64.90
7 purchase totals =	$868.24		$929.1110	$929.11	$929.20	$929.20