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	$225.27	6.590%	$240.1153	$240.12	$240.10	$240.10
Purchase #2	$222.42	12.647%	$250.5495	$250.55	$250.55	$250.50
Purchase #3	$24.76	3.291%	$25.5749	$25.57	$25.55	$25.60
Purchase #4	$200.64	12.484%	$225.6879	$225.69	$225.70	$225.70
Purchase #5	$143.88	4.428%	$150.251	$150.25	$150.25	$150.30
Purchase #6	$158.40	5.148%	$166.5544	$166.55	$166.55	$166.60
Purchase #7	$37.92	11.642%	$42.3346	$42.33	$42.35	$42.30
7 purchase totals =	$1,013.29		$1,101.0676	$1,101.06	$1,101.05	$1,101.10