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	$79.69	3.380%	$82.3835	$82.38	$82.40	$82.40
Purchase #2	$86.65	3.265%	$89.4791	$89.48	$89.50	$89.50
Purchase #3	$58.76	10.439%	$64.894	$64.89	$64.90	$64.90
Purchase #4	$91.58	10.614%	$101.3003	$101.30	$101.30	$101.30
Purchase #5	$39.54	7.279%	$42.4181	$42.42	$42.40	$42.40
Purchase #6	$77.44	9.327%	$84.6628	$84.66	$84.65	$84.70
Purchase #7	$142.57	4.195%	$148.5508	$148.55	$148.55	$148.60
7 purchase totals =	$576.23		$613.6886	$613.68	$613.70	$613.80