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	$50.90	8.569%	$55.2616	$55.26	$55.25	$55.30
Purchase #2	$11.28	9.417%	$12.3422	$12.34	$12.35	$12.30
Purchase #3	$156.57	6.112%	$166.1396	$166.14	$166.15	$166.10
Purchase #4	$250.65	10.154%	$276.101	$276.10	$276.10	$276.10
Purchase #5	$20.59	11.332%	$22.9233	$22.92	$22.90	$22.90
Purchase #6	$125.45	4.471%	$131.0589	$131.06	$131.05	$131.10
Purchase #7	$223.61	4.470%	$233.6054	$233.61	$233.60	$233.60
7 purchase totals =	$839.05		$897.4320	$897.43	$897.40	$897.40