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	$149.76	8.489%	$162.4731	$162.47	$162.45	$162.50
Purchase #2	$245.89	6.851%	$262.7359	$262.74	$262.75	$262.70
Purchase #3	$244.90	8.410%	$265.4961	$265.50	$265.50	$265.50
Purchase #4	$27.94	5.137%	$29.3753	$29.38	$29.40	$29.40
Purchase #5	$178.60	9.333%	$195.2687	$195.27	$195.25	$195.30
Purchase #6	$187.31	3.796%	$194.4203	$194.42	$194.40	$194.40
Purchase #7	$53.89	13.771%	$61.3112	$61.31	$61.30	$61.30
7 purchase totals =	$1,088.29		$1,171.0806	$1,171.09	$1,171.05	$1,171.10