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	$35.87	7.727%	$38.6417	$38.64	$38.65	$38.60
Purchase #2	$152.87	11.383%	$170.2712	$170.27	$170.25	$170.30
Purchase #3	$166.33	11.234%	$185.0155	$185.02	$185.00	$185.00
Purchase #4	$188.67	4.222%	$196.6356	$196.64	$196.65	$196.60
Purchase #5	$41.78	7.628%	$44.967	$44.97	$44.95	$45.00
Purchase #6	$22.54	8.144%	$24.3757	$24.38	$24.40	$24.40
Purchase #7	$55.59	13.771%	$63.2453	$63.25	$63.25	$63.20
7 purchase totals =	$663.65		$723.1520	$723.17	$723.15	$723.10