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	$69.28	4.574%	$72.4489	$72.45	$72.45	$72.40
Purchase #2	$171.28	7.388%	$183.9342	$183.93	$183.95	$183.90
Purchase #3	$91.97	4.583%	$96.185	$96.19	$96.20	$96.20
Purchase #4	$104.41	4.538%	$109.1481	$109.15	$109.15	$109.10
Purchase #5	$224.59	11.639%	$250.73	$250.73	$250.75	$250.70
Purchase #6	$48.70	10.636%	$53.8797	$53.88	$53.90	$53.90
Purchase #7	$109.30	9.211%	$119.3676	$119.37	$119.35	$119.40
7 purchase totals =	$819.53		$885.6935	$885.70	$885.75	$885.60