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	$151.74	3.293%	$156.7368	$156.74	$156.75	$156.70
Purchase #2	$51.96	13.509%	$58.9793	$58.98	$59.00	$59.00
Purchase #3	$213.91	13.838%	$243.5109	$243.51	$243.50	$243.50
Purchase #4	$174.98	6.223%	$185.869	$185.87	$185.85	$185.90
Purchase #5	$123.33	13.250%	$139.6712	$139.67	$139.65	$139.70
Purchase #6	$54.80	11.584%	$61.148	$61.15	$61.15	$61.10
Purchase #7	$141.52	3.242%	$146.1081	$146.11	$146.10	$146.10
7 purchase totals =	$912.24		$992.0233	$992.03	$992.00	$992.00