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	$182.83	5.455%	$192.8034	$192.80	$192.80	$192.80
Purchase #2	$34.81	7.508%	$37.4235	$37.42	$37.40	$37.40
Purchase #3	$55.88	12.315%	$62.7616	$62.76	$62.75	$62.80
Purchase #4	$33.52	6.732%	$35.7766	$35.78	$35.80	$35.80
Purchase #5	$118.53	12.229%	$133.025	$133.03	$133.05	$133.00
Purchase #6	$245.82	4.190%	$256.1199	$256.12	$256.10	$256.10
Purchase #7	$249.70	5.586%	$263.6482	$263.65	$263.65	$263.60
7 purchase totals =	$921.09		$981.5582	$981.56	$981.55	$981.50