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	$212.92	7.846%	$229.6257	$229.63	$229.65	$229.60
Purchase #2	$191.53	12.657%	$215.772	$215.77	$215.75	$215.80
Purchase #3	$104.97	13.804%	$119.4601	$119.46	$119.45	$119.50
Purchase #4	$32.60	7.431%	$35.0225	$35.02	$35.00	$35.00
Purchase #5	$96.43	3.404%	$99.7125	$99.71	$99.70	$99.70
Purchase #6	$36.72	12.385%	$41.2678	$41.27	$41.25	$41.30
Purchase #7	$152.26	13.215%	$172.3812	$172.38	$172.40	$172.40
7 purchase totals =	$827.43		$913.2418	$913.24	$913.20	$913.30