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	$31.66	12.609%	$35.652	$35.65	$35.65	$35.70
Purchase #2	$57.45	7.759%	$61.9075	$61.91	$61.90	$61.90
Purchase #3	$55.51	7.858%	$59.872	$59.87	$59.85	$59.90
Purchase #4	$97.33	6.814%	$103.9621	$103.96	$103.95	$104.00
Purchase #5	$233.27	12.846%	$263.2359	$263.24	$263.25	$263.20
Purchase #6	$29.74	7.593%	$31.9982	$32.00	$32.00	$32.00
Purchase #7	$225.91	4.433%	$235.9246	$235.92	$235.90	$235.90
7 purchase totals =	$730.87		$792.5523	$792.55	$792.50	$792.60