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	$71.44	8.823%	$77.7432	$77.74	$77.75	$77.70
Purchase #2	$220.62	13.283%	$249.925	$249.93	$249.95	$249.90
Purchase #3	$219.50	10.374%	$242.2709	$242.27	$242.25	$242.30
Purchase #4	$150.87	12.220%	$169.3063	$169.31	$169.30	$169.30
Purchase #5	$92.89	8.829%	$101.0913	$101.09	$101.10	$101.10
Purchase #6	$94.54	5.408%	$99.6527	$99.65	$99.65	$99.70
Purchase #7	$91.87	9.388%	$100.4948	$100.49	$100.50	$100.50
7 purchase totals =	$941.73		$1,040.4842	$1,040.48	$1,040.50	$1,040.50