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	$200.66	11.802%	$224.3419	$224.34	$224.35	$224.30
Purchase #2	$49.33	9.122%	$53.8299	$53.83	$53.85	$53.80
Purchase #3	$134.58	7.352%	$144.4743	$144.47	$144.45	$144.50
Purchase #4	$129.34	3.125%	$133.3819	$133.38	$133.40	$133.40
Purchase #5	$204.46	13.182%	$231.4119	$231.41	$231.40	$231.40
Purchase #6	$174.85	5.377%	$184.2517	$184.25	$184.25	$184.30
Purchase #7	$78.38	5.483%	$82.6776	$82.68	$82.70	$82.70
7 purchase totals =	$971.60		$1,054.3692	$1,054.36	$1,054.40	$1,054.40