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	$209.28	9.508%	$229.1783	$229.18	$229.20	$229.20
Purchase #2	$98.83	3.494%	$102.2831	$102.28	$102.30	$102.30
Purchase #3	$125.72	9.336%	$137.4572	$137.46	$137.45	$137.50
Purchase #4	$66.80	11.574%	$74.5314	$74.53	$74.55	$74.50
Purchase #5	$123.91	11.234%	$137.83	$137.83	$137.85	$137.80
Purchase #6	$165.56	5.171%	$174.1211	$174.12	$174.10	$174.10
Purchase #7	$207.69	10.167%	$228.8058	$228.81	$228.80	$228.80
7 purchase totals =	$997.79		$1,084.2069	$1,084.21	$1,084.25	$1,084.20