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	$73.65	6.686%	$78.5742	$78.57	$78.55	$78.60
Purchase #2	$29.37	7.268%	$31.5046	$31.50	$31.50	$31.50
Purchase #3	$185.88	13.494%	$210.9626	$210.96	$210.95	$211.00
Purchase #4	$137.81	10.778%	$152.6632	$152.66	$152.65	$152.70
Purchase #5	$236.70	3.681%	$245.4129	$245.41	$245.40	$245.40
Purchase #6	$206.78	13.718%	$235.1461	$235.15	$235.15	$235.10
Purchase #7	$228.47	5.147%	$240.2294	$240.23	$240.25	$240.20
7 purchase totals =	$1,098.66		$1,194.4930	$1,194.48	$1,194.45	$1,194.50