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	$181.63	4.415%	$189.649	$189.65	$189.65	$189.60
Purchase #2	$113.34	3.191%	$116.9567	$116.96	$116.95	$117.00
Purchase #3	$203.85	9.242%	$222.6898	$222.69	$222.70	$222.70
Purchase #4	$200.30	4.630%	$209.5739	$209.57	$209.55	$209.60
Purchase #5	$202.74	4.524%	$211.912	$211.91	$211.90	$211.90
Purchase #6	$66.57	9.390%	$72.8209	$72.82	$72.80	$72.80
Purchase #7	$155.62	6.529%	$165.7804	$165.78	$165.80	$165.80
7 purchase totals =	$1,124.05		$1,189.3827	$1,189.38	$1,189.35	$1,189.40