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	$180.83	5.216%	$190.2621	$190.26	$190.25	$190.30
Purchase #2	$28.92	7.401%	$31.0604	$31.06	$31.05	$31.10
Purchase #3	$73.57	7.302%	$78.9421	$78.94	$78.95	$78.90
Purchase #4	$29.42	3.414%	$30.4244	$30.42	$30.40	$30.40
Purchase #5	$65.65	8.436%	$71.1882	$71.19	$71.20	$71.20
Purchase #6	$70.70	11.231%	$78.6403	$78.64	$78.65	$78.60
Purchase #7	$139.40	3.785%	$144.6763	$144.68	$144.70	$144.70
7 purchase totals =	$588.49		$625.1938	$625.19	$625.20	$625.20