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	$148.27	4.216%	$154.5211	$154.52	$154.50	$154.50
Purchase #2	$130.74	13.585%	$148.501	$148.50	$148.50	$148.50
Purchase #3	$171.55	12.190%	$192.4619	$192.46	$192.45	$192.50
Purchase #4	$165.49	7.238%	$177.4682	$177.47	$177.45	$177.50
Purchase #5	$158.26	6.775%	$168.9821	$168.98	$169.00	$169.00
Purchase #6	$37.83	6.597%	$40.3256	$40.33	$40.35	$40.30
Purchase #7	$203.56	8.527%	$220.9176	$220.92	$220.90	$220.90
7 purchase totals =	$1,015.70		$1,103.1775	$1,103.18	$1,103.15	$1,103.20