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	$148.58	5.304%	$156.4607	$156.46	$156.45	$156.50
Purchase #2	$215.35	7.348%	$231.1739	$231.17	$231.15	$231.20
Purchase #3	$233.91	6.491%	$249.0931	$249.09	$249.10	$249.10
Purchase #4	$30.71	4.550%	$32.1073	$32.11	$32.10	$32.10
Purchase #5	$68.72	4.853%	$72.055	$72.06	$72.05	$72.10
Purchase #6	$188.73	13.398%	$214.016	$214.02	$214.00	$214.00
Purchase #7	$188.44	3.667%	$195.3501	$195.35	$195.35	$195.40
7 purchase totals =	$1,074.44		$1,150.2561	$1,150.26	$1,150.20	$1,150.40