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	$96.54	10.148%	$106.3369	$106.34	$106.35	$106.30
Purchase #2	$188.58	8.220%	$204.0813	$204.08	$204.10	$204.10
Purchase #3	$164.41	3.117%	$169.5347	$169.53	$169.55	$169.50
Purchase #4	$176.40	8.591%	$191.5545	$191.55	$191.55	$191.60
Purchase #5	$73.77	11.377%	$82.1628	$82.16	$82.15	$82.20
Purchase #6	$176.33	11.504%	$196.615	$196.62	$196.60	$196.60
Purchase #7	$129.39	7.790%	$139.4695	$139.47	$139.45	$139.50
7 purchase totals =	$1,005.42		$1,089.7547	$1,089.75	$1,089.75	$1,089.80