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	$139.33	6.272%	$148.0688	$148.07	$148.05	$148.10
Purchase #2	$177.89	10.334%	$196.2732	$196.27	$196.25	$196.30
Purchase #3	$245.42	4.612%	$256.7388	$256.74	$256.75	$256.70
Purchase #4	$54.64	6.769%	$58.3386	$58.34	$58.35	$58.30
Purchase #5	$92.28	10.230%	$101.7202	$101.72	$101.70	$101.70
Purchase #6	$53.84	8.306%	$58.312	$58.31	$58.30	$58.30
Purchase #7	$85.62	4.200%	$89.216	$89.22	$89.20	$89.20
7 purchase totals =	$849.02		$908.6676	$908.67	$908.60	$908.60