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	$19.43	4.590%	$20.3218	$20.32	$20.30	$20.30
Purchase #2	$247.72	8.755%	$269.4079	$269.41	$269.40	$269.40
Purchase #3	$31.96	10.419%	$35.2899	$35.29	$35.30	$35.30
Purchase #4	$233.98	8.663%	$254.2497	$254.25	$254.25	$254.20
Purchase #5	$215.39	12.849%	$243.0655	$243.07	$243.05	$243.10
Purchase #6	$114.63	10.384%	$126.5332	$126.53	$126.55	$126.50
Purchase #7	$190.35	12.298%	$213.7592	$213.76	$213.75	$213.80
7 purchase totals =	$1,053.46		$1,162.6272	$1,162.63	$1,162.60	$1,162.60