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	$93.66	5.205%	$98.535	$98.54	$98.55	$98.50
Purchase #2	$62.87	5.504%	$66.3304	$66.33	$66.35	$66.30
Purchase #3	$59.28	3.411%	$61.302	$61.30	$61.30	$61.30
Purchase #4	$62.85	11.435%	$70.0369	$70.04	$70.05	$70.00
Purchase #5	$238.70	10.552%	$263.8876	$263.89	$263.90	$263.90
Purchase #6	$186.42	3.282%	$192.5383	$192.54	$192.55	$192.50
Purchase #7	$176.30	7.535%	$189.5842	$189.58	$189.60	$189.60
7 purchase totals =	$880.08		$942.2144	$942.22	$942.30	$942.10