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	$75.83	8.443%	$82.2323	$82.23	$82.25	$82.20
Purchase #2	$100.56	5.784%	$106.3764	$106.38	$106.40	$106.40
Purchase #3	$81.73	9.273%	$89.3088	$89.31	$89.30	$89.30
Purchase #4	$215.82	11.471%	$240.5767	$240.58	$240.60	$240.60
Purchase #5	$130.28	12.562%	$146.6458	$146.65	$146.65	$146.60
Purchase #6	$244.45	8.524%	$265.2869	$265.29	$265.30	$265.30
Purchase #7	$145.29	3.561%	$150.4638	$150.46	$150.45	$150.50
7 purchase totals =	$993.96		$1,080.8907	$1,080.90	$1,080.95	$1,080.90