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	$166.75	12.461%	$187.5287	$187.53	$187.55	$187.50
Purchase #2	$28.78	3.427%	$29.7663	$29.77	$29.75	$29.80
Purchase #3	$99.32	3.816%	$103.1101	$103.11	$103.10	$103.10
Purchase #4	$174.45	4.823%	$182.8637	$182.86	$182.85	$182.90
Purchase #5	$105.90	9.568%	$116.0325	$116.03	$116.05	$116.00
Purchase #6	$243.53	8.457%	$264.1253	$264.13	$264.15	$264.10
Purchase #7	$247.95	6.290%	$263.5461	$263.55	$263.55	$263.50
7 purchase totals =	$1,066.68		$1,146.9727	$1,146.98	$1,147.00	$1,146.90