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	$104.75	6.614%	$111.6782	$111.68	$111.70	$111.70
Purchase #2	$197.78	9.607%	$216.7807	$216.78	$216.80	$216.80
Purchase #3	$213.32	5.805%	$225.7032	$225.70	$225.70	$225.70
Purchase #4	$131.86	11.580%	$147.1294	$147.13	$147.15	$147.10
Purchase #5	$150.82	3.630%	$156.2948	$156.29	$156.30	$156.30
Purchase #6	$99.75	13.190%	$112.907	$112.91	$112.90	$112.90
Purchase #7	$165.33	7.223%	$177.2718	$177.27	$177.25	$177.30
7 purchase totals =	$1,063.61		$1,147.7651	$1,147.76	$1,147.80	$1,147.80