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	$50.41	10.213%	$55.5584	$55.56	$55.55	$55.60
Purchase #2	$150.30	3.525%	$155.5981	$155.60	$155.60	$155.60
Purchase #3	$142.79	6.391%	$151.9157	$151.92	$151.90	$151.90
Purchase #4	$220.43	13.564%	$250.3291	$250.33	$250.35	$250.30
Purchase #5	$223.96	13.661%	$254.5552	$254.56	$254.55	$254.60
Purchase #6	$211.67	7.793%	$228.1654	$228.17	$228.15	$228.20
Purchase #7	$45.37	13.790%	$51.6265	$51.63	$51.65	$51.60
7 purchase totals =	$1,044.93		$1,147.7484	$1,147.77	$1,147.75	$1,147.80