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	$135.40	12.388%	$152.1734	$152.17	$152.15	$152.20
Purchase #2	$106.50	10.836%	$118.0403	$118.04	$118.05	$118.00
Purchase #3	$244.96	6.255%	$260.2822	$260.28	$260.30	$260.30
Purchase #4	$189.94	12.485%	$213.654	$213.65	$213.65	$213.70
Purchase #5	$54.83	7.129%	$58.7388	$58.74	$58.75	$58.70
Purchase #6	$67.44	7.331%	$72.384	$72.38	$72.40	$72.40
Purchase #7	$215.66	4.321%	$224.9787	$224.98	$225.00	$225.00
7 purchase totals =	$1,014.73		$1,100.2514	$1,100.24	$1,100.30	$1,100.30