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	$243.77	10.467%	$269.2854	$269.29	$269.30	$269.30
Purchase #2	$133.85	9.754%	$146.9057	$146.91	$146.90	$146.90
Purchase #3	$28.37	12.390%	$31.885	$31.89	$31.90	$31.90
Purchase #4	$80.43	10.799%	$89.1156	$89.12	$89.10	$89.10
Purchase #5	$88.36	6.742%	$94.3172	$94.32	$94.30	$94.30
Purchase #6	$250.95	12.420%	$282.118	$282.12	$282.10	$282.10
Purchase #7	$96.48	10.481%	$106.5921	$106.59	$106.60	$106.60
7 purchase totals =	$922.21		$1,020.2190	$1,020.24	$1,020.20	$1,020.20