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	$177.56	4.618%	$185.7597	$185.76	$185.75	$185.80
Purchase #2	$74.78	10.108%	$82.3388	$82.34	$82.35	$82.30
Purchase #3	$234.37	10.774%	$259.621	$259.62	$259.60	$259.60
Purchase #4	$21.42	4.870%	$22.4632	$22.46	$22.45	$22.50
Purchase #5	$95.43	13.829%	$108.627	$108.63	$108.65	$108.60
Purchase #6	$120.89	4.147%	$125.9033	$125.90	$125.90	$125.90
Purchase #7	$233.87	11.345%	$260.4026	$260.40	$260.40	$260.40
7 purchase totals =	$958.32		$1,045.1156	$1,045.11	$1,045.10	$1,045.10