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	$82.47	10.521%	$91.1467	$91.15	$91.15	$91.10
Purchase #2	$105.73	5.650%	$111.7037	$111.70	$111.70	$111.70
Purchase #3	$127.39	5.819%	$134.8028	$134.80	$134.80	$134.80
Purchase #4	$59.61	6.377%	$63.4113	$63.41	$63.40	$63.40
Purchase #5	$149.74	8.218%	$162.0456	$162.05	$162.05	$162.00
Purchase #6	$146.91	11.781%	$164.2175	$164.22	$164.20	$164.20
Purchase #7	$112.38	5.820%	$118.9205	$118.92	$118.90	$118.90
7 purchase totals =	$784.23		$846.2481	$846.25	$846.20	$846.10