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	$117.84	3.727%	$122.2319	$122.23	$122.25	$122.20
Purchase #2	$28.64	3.300%	$29.5851	$29.59	$29.60	$29.60
Purchase #3	$98.41	7.242%	$105.5369	$105.54	$105.55	$105.50
Purchase #4	$93.99	6.641%	$100.2319	$100.23	$100.25	$100.20
Purchase #5	$239.71	7.112%	$256.7582	$256.76	$256.75	$256.80
Purchase #6	$123.67	5.525%	$130.5028	$130.50	$130.50	$130.50
Purchase #7	$165.80	11.644%	$185.1058	$185.11	$185.10	$185.10
7 purchase totals =	$868.06		$929.9526	$929.96	$930.00	$929.90