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	$147.85	13.301%	$167.5155	$167.52	$167.50	$167.50
Purchase #2	$188.90	13.446%	$214.2995	$214.30	$214.30	$214.30
Purchase #3	$28.56	8.763%	$31.0627	$31.06	$31.05	$31.10
Purchase #4	$134.91	9.599%	$147.86	$147.86	$147.85	$147.90
Purchase #5	$165.27	4.531%	$172.7584	$172.76	$172.75	$172.80
Purchase #6	$187.50	11.501%	$209.0644	$209.06	$209.05	$209.10
Purchase #7	$132.42	11.145%	$147.1782	$147.18	$147.20	$147.20
7 purchase totals =	$985.41		$1,089.7387	$1,089.74	$1,089.70	$1,089.90