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	$170.81	6.462%	$181.8477	$181.85	$181.85	$181.80
Purchase #2	$84.74	8.680%	$92.0954	$92.10	$92.10	$92.10
Purchase #3	$56.70	7.829%	$61.139	$61.14	$61.15	$61.10
Purchase #4	$188.29	12.336%	$211.5175	$211.52	$211.50	$211.50
Purchase #5	$154.32	7.348%	$165.6594	$165.66	$165.65	$165.70
Purchase #6	$134.99	11.681%	$150.7582	$150.76	$150.75	$150.80
Purchase #7	$103.33	11.855%	$115.5798	$115.58	$115.60	$115.60
7 purchase totals =	$893.18		$978.5970	$978.61	$978.60	$978.60