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	$171.30	6.339%	$182.1587	$182.16	$182.15	$182.20
Purchase #2	$48.56	5.283%	$51.1254	$51.13	$51.15	$51.10
Purchase #3	$73.54	11.674%	$82.1251	$82.13	$82.15	$82.10
Purchase #4	$170.26	6.121%	$180.6816	$180.68	$180.70	$180.70
Purchase #5	$215.81	10.662%	$238.8197	$238.82	$238.80	$238.80
Purchase #6	$187.91	4.673%	$196.691	$196.69	$196.70	$196.70
Purchase #7	$33.28	13.626%	$37.8147	$37.81	$37.80	$37.80
7 purchase totals =	$900.66		$969.4162	$969.42	$969.45	$969.40