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	$176.70	4.870%	$185.3053	$185.31	$185.30	$185.30
Purchase #2	$165.46	12.518%	$186.1723	$186.17	$186.15	$186.20
Purchase #3	$41.59	9.477%	$45.5315	$45.53	$45.55	$45.50
Purchase #4	$132.81	8.694%	$144.3565	$144.36	$144.35	$144.40
Purchase #5	$39.69	9.396%	$43.4193	$43.42	$43.40	$43.40
Purchase #6	$214.92	6.728%	$229.3798	$229.38	$229.40	$229.40
Purchase #7	$133.69	6.195%	$141.9721	$141.97	$141.95	$142.00
7 purchase totals =	$904.86		$976.1368	$976.14	$976.10	$976.20