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	$172.65	3.245%	$178.2525	$178.25	$178.25	$178.30
Purchase #2	$120.69	8.847%	$131.3674	$131.37	$131.35	$131.40
Purchase #3	$118.33	11.393%	$131.8113	$131.81	$131.80	$131.80
Purchase #4	$124.30	3.111%	$128.167	$128.17	$128.15	$128.20
Purchase #5	$66.74	10.243%	$73.5762	$73.58	$73.60	$73.60
Purchase #6	$156.87	6.345%	$166.8234	$166.82	$166.80	$166.80
Purchase #7	$33.84	11.777%	$37.8253	$37.83	$37.85	$37.80
7 purchase totals =	$793.42		$847.8231	$847.83	$847.80	$847.90