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	$186.72	10.794%	$206.8746	$206.87	$206.85	$206.90
Purchase #2	$26.33	13.517%	$29.889	$29.89	$29.90	$29.90
Purchase #3	$82.91	13.736%	$94.2985	$94.30	$94.30	$94.30
Purchase #4	$178.58	9.804%	$196.088	$196.09	$196.10	$196.10
Purchase #5	$185.57	5.431%	$195.6483	$195.65	$195.65	$195.60
Purchase #6	$94.56	3.470%	$97.8412	$97.84	$97.85	$97.80
Purchase #7	$225.98	7.762%	$243.5206	$243.52	$243.50	$243.50
7 purchase totals =	$980.65		$1,064.1602	$1,064.16	$1,064.15	$1,064.10