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	$227.29	10.418%	$250.9691	$250.97	$250.95	$251.00
Purchase #2	$142.66	5.224%	$150.1126	$150.11	$150.10	$150.10
Purchase #3	$54.77	13.279%	$62.0429	$62.04	$62.05	$62.00
Purchase #4	$74.73	7.219%	$80.1248	$80.12	$80.10	$80.10
Purchase #5	$156.66	10.133%	$172.5344	$172.53	$172.55	$172.50
Purchase #6	$233.37	4.821%	$244.6208	$244.62	$244.60	$244.60
Purchase #7	$185.57	3.687%	$192.412	$192.41	$192.40	$192.40
7 purchase totals =	$1,075.05		$1,152.8166	$1,152.80	$1,152.75	$1,152.70