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	$185.37	6.232%	$196.9223	$196.92	$196.90	$196.90
Purchase #2	$245.64	12.652%	$276.7184	$276.72	$276.70	$276.70
Purchase #3	$145.85	11.314%	$162.3515	$162.35	$162.35	$162.40
Purchase #4	$204.91	11.118%	$227.6919	$227.69	$227.70	$227.70
Purchase #5	$213.89	7.411%	$229.7414	$229.74	$229.75	$229.70
Purchase #6	$233.48	12.797%	$263.3584	$263.36	$263.35	$263.40
Purchase #7	$56.72	4.600%	$59.3291	$59.33	$59.35	$59.30
7 purchase totals =	$1,285.86		$1,416.1130	$1,416.11	$1,416.10	$1,416.10