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	$243.73	4.563%	$254.8514	$254.85	$254.85	$254.90
Purchase #2	$86.83	3.695%	$90.0384	$90.04	$90.05	$90.00
Purchase #3	$95.98	11.152%	$106.6837	$106.68	$106.70	$106.70
Purchase #4	$138.33	4.350%	$144.3474	$144.35	$144.35	$144.30
Purchase #5	$148.91	10.840%	$165.0518	$165.05	$165.05	$165.10
Purchase #6	$214.47	3.122%	$221.1658	$221.17	$221.15	$221.20
Purchase #7	$52.30	13.492%	$59.3563	$59.36	$59.35	$59.40
7 purchase totals =	$980.55		$1,041.4948	$1,041.50	$1,041.50	$1,041.60