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	$79.59	4.609%	$83.2583	$83.26	$83.25	$83.30
Purchase #2	$23.85	5.459%	$25.152	$25.15	$25.15	$25.20
Purchase #3	$194.86	8.863%	$212.1304	$212.13	$212.15	$212.10
Purchase #4	$188.28	10.790%	$208.5954	$208.60	$208.60	$208.60
Purchase #5	$62.74	13.831%	$71.4176	$71.42	$71.40	$71.40
Purchase #6	$197.81	12.784%	$223.098	$223.10	$223.10	$223.10
Purchase #7	$192.76	10.435%	$212.8745	$212.87	$212.85	$212.90
7 purchase totals =	$939.89		$1,036.5262	$1,036.53	$1,036.50	$1,036.60