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	$64.56	8.711%	$70.1838	$70.18	$70.20	$70.20
Purchase #2	$26.38	7.484%	$28.3543	$28.35	$28.35	$28.40
Purchase #3	$208.25	8.106%	$225.1307	$225.13	$225.15	$225.10
Purchase #4	$246.72	11.486%	$275.0583	$275.06	$275.05	$275.10
Purchase #5	$185.56	5.743%	$196.2167	$196.22	$196.20	$196.20
Purchase #6	$250.33	7.276%	$268.544	$268.54	$268.55	$268.50
Purchase #7	$160.72	8.658%	$174.6351	$174.64	$174.65	$174.60
7 purchase totals =	$1,142.52		$1,238.1229	$1,238.12	$1,238.15	$1,238.10