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	$94.39	5.310%	$99.4021	$99.40	$99.40	$99.40
Purchase #2	$248.76	8.288%	$269.3772	$269.38	$269.40	$269.40
Purchase #3	$53.27	5.410%	$56.1519	$56.15	$56.15	$56.20
Purchase #4	$175.29	10.773%	$194.174	$194.17	$194.15	$194.20
Purchase #5	$82.89	10.224%	$91.3647	$91.36	$91.35	$91.40
Purchase #6	$99.95	11.296%	$111.2404	$111.24	$111.25	$111.20
Purchase #7	$206.28	8.102%	$222.9928	$222.99	$223.00	$223.00
7 purchase totals =	$960.83		$1,044.7031	$1,044.69	$1,044.70	$1,044.80