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	$65.30	11.760%	$72.9793	$72.98	$73.00	$73.00
Purchase #2	$138.71	12.247%	$155.6978	$155.70	$155.70	$155.70
Purchase #3	$32.84	13.759%	$37.3585	$37.36	$37.35	$37.40
Purchase #4	$187.91	4.735%	$196.8075	$196.81	$196.80	$196.80
Purchase #5	$121.68	11.871%	$136.1246	$136.12	$136.10	$136.10
Purchase #6	$22.95	10.155%	$25.2806	$25.28	$25.30	$25.30
Purchase #7	$184.82	6.316%	$196.4932	$196.49	$196.50	$196.50
7 purchase totals =	$754.21		$820.7415	$820.74	$820.75	$820.80