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	$95.87	9.375%	$104.8578	$104.86	$104.85	$104.90
Purchase #2	$84.67	8.604%	$91.955	$91.96	$91.95	$92.00
Purchase #3	$145.92	12.839%	$164.6547	$164.65	$164.65	$164.70
Purchase #4	$221.85	10.705%	$245.599	$245.60	$245.60	$245.60
Purchase #5	$69.55	12.447%	$78.2069	$78.21	$78.20	$78.20
Purchase #6	$135.25	8.399%	$146.6096	$146.61	$146.60	$146.60
Purchase #7	$39.94	6.521%	$42.5445	$42.54	$42.55	$42.50
7 purchase totals =	$793.05		$874.4275	$874.43	$874.40	$874.50