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	$154.44	10.808%	$171.1319	$171.13	$171.15	$171.10
Purchase #2	$97.31	6.449%	$103.5855	$103.59	$103.60	$103.60
Purchase #3	$120.31	9.141%	$131.3075	$131.31	$131.30	$131.30
Purchase #4	$37.35	5.763%	$39.5025	$39.50	$39.50	$39.50
Purchase #5	$55.94	9.621%	$61.322	$61.32	$61.30	$61.30
Purchase #6	$96.41	10.355%	$106.3933	$106.39	$106.40	$106.40
Purchase #7	$181.54	3.574%	$188.0282	$188.03	$188.05	$188.00
7 purchase totals =	$743.30		$801.2709	$801.27	$801.30	$801.20