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	$133.85	5.369%	$141.0364	$141.04	$141.05	$141.00
Purchase #2	$144.87	3.479%	$149.91	$149.91	$149.90	$149.90
Purchase #3	$199.75	11.830%	$223.3804	$223.38	$223.40	$223.40
Purchase #4	$77.48	3.863%	$80.4731	$80.47	$80.45	$80.50
Purchase #5	$133.37	6.719%	$142.3311	$142.33	$142.35	$142.30
Purchase #6	$237.77	4.630%	$248.7788	$248.78	$248.80	$248.80
Purchase #7	$84.69	7.832%	$91.3229	$91.32	$91.30	$91.30
7 purchase totals =	$1,011.78		$1,077.2327	$1,077.23	$1,077.25	$1,077.20