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	$221.59	5.691%	$234.2007	$234.20	$234.20	$234.20
Purchase #2	$67.91	4.677%	$71.0862	$71.09	$71.10	$71.10
Purchase #3	$40.41	9.608%	$44.2926	$44.29	$44.30	$44.30
Purchase #4	$82.34	4.747%	$86.2487	$86.25	$86.25	$86.20
Purchase #5	$193.89	3.315%	$200.3175	$200.32	$200.30	$200.30
Purchase #6	$111.57	4.272%	$116.3363	$116.34	$116.35	$116.30
Purchase #7	$236.82	5.733%	$250.3969	$250.40	$250.40	$250.40
7 purchase totals =	$954.53		$1,002.8789	$1,002.89	$1,002.90	$1,002.80