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	$247.73	6.851%	$264.702	$264.70	$264.70	$264.70
Purchase #2	$73.51	6.584%	$78.3499	$78.35	$78.35	$78.30
Purchase #3	$18.92	11.723%	$21.138	$21.14	$21.15	$21.10
Purchase #4	$78.35	3.782%	$81.3132	$81.31	$81.30	$81.30
Purchase #5	$210.96	3.234%	$217.7824	$217.78	$217.80	$217.80
Purchase #6	$133.90	9.398%	$146.4839	$146.48	$146.50	$146.50
Purchase #7	$174.42	9.753%	$191.4312	$191.43	$191.45	$191.40
7 purchase totals =	$937.79		$1,001.2006	$1,001.19	$1,001.25	$1,001.10