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	$68.45	4.381%	$71.4488	$71.45	$71.45	$71.40
Purchase #2	$70.84	9.130%	$77.3077	$77.31	$77.30	$77.30
Purchase #3	$183.83	8.685%	$199.7956	$199.80	$199.80	$199.80
Purchase #4	$56.43	9.726%	$61.9184	$61.92	$61.90	$61.90
Purchase #5	$222.52	11.857%	$248.9042	$248.90	$248.90	$248.90
Purchase #6	$62.75	4.535%	$65.5957	$65.60	$65.60	$65.60
Purchase #7	$119.39	11.480%	$133.096	$133.10	$133.10	$133.10
7 purchase totals =	$784.21		$858.0664	$858.08	$858.05	$858.00