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	$39.83	13.820%	$45.3345	$45.33	$45.35	$45.30
Purchase #2	$109.87	10.383%	$121.2778	$121.28	$121.30	$121.30
Purchase #3	$32.89	8.201%	$35.5873	$35.59	$35.60	$35.60
Purchase #4	$248.98	8.318%	$269.6902	$269.69	$269.70	$269.70
Purchase #5	$39.96	7.258%	$42.8603	$42.86	$42.85	$42.90
Purchase #6	$88.75	7.824%	$95.6938	$95.69	$95.70	$95.70
Purchase #7	$249.51	6.336%	$265.319	$265.32	$265.30	$265.30
7 purchase totals =	$809.79		$875.7629	$875.76	$875.80	$875.80