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	$244.76	3.539%	$253.4221	$253.42	$253.40	$253.40
Purchase #2	$118.27	7.315%	$126.9215	$126.92	$126.90	$126.90
Purchase #3	$129.62	5.800%	$137.138	$137.14	$137.15	$137.10
Purchase #4	$145.69	4.677%	$152.5039	$152.50	$152.50	$152.50
Purchase #5	$192.83	9.191%	$210.553	$210.55	$210.55	$210.60
Purchase #6	$179.61	8.300%	$194.5176	$194.52	$194.50	$194.50
Purchase #7	$5.75	10.149%	$6.3336	$6.33	$6.35	$6.30
7 purchase totals =	$1,016.53		$1,081.3897	$1,081.38	$1,081.35	$1,081.30