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	$47.65	3.543%	$49.3382	$49.34	$49.35	$49.30
Purchase #2	$209.43	9.739%	$229.8264	$229.83	$229.85	$229.80
Purchase #3	$135.62	4.345%	$141.5127	$141.51	$141.50	$141.50
Purchase #4	$145.92	3.850%	$151.5379	$151.54	$151.55	$151.50
Purchase #5	$165.91	9.630%	$181.8871	$181.89	$181.90	$181.90
Purchase #6	$179.71	6.312%	$191.0533	$191.05	$191.05	$191.10
Purchase #7	$151.54	6.421%	$161.2704	$161.27	$161.25	$161.30
7 purchase totals =	$1,035.78		$1,106.4260	$1,106.43	$1,106.45	$1,106.40