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	$165.86	4.547%	$173.4017	$173.40	$173.40	$173.40
Purchase #2	$101.88	13.475%	$115.6083	$115.61	$115.60	$115.60
Purchase #3	$19.71	13.609%	$22.3923	$22.39	$22.40	$22.40
Purchase #4	$155.81	11.208%	$173.2732	$173.27	$173.25	$173.30
Purchase #5	$144.59	3.833%	$150.1321	$150.13	$150.15	$150.10
Purchase #6	$239.66	12.142%	$268.7595	$268.76	$268.75	$268.80
Purchase #7	$172.81	9.535%	$189.2874	$189.29	$189.30	$189.30
7 purchase totals =	$1,000.32		$1,092.8545	$1,092.85	$1,092.85	$1,092.90