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	$134.79	10.424%	$148.8405	$148.84	$148.85	$148.80
Purchase #2	$74.56	3.435%	$77.1211	$77.12	$77.10	$77.10
Purchase #3	$141.77	7.161%	$151.9221	$151.92	$151.90	$151.90
Purchase #4	$17.25	6.181%	$18.3162	$18.32	$18.30	$18.30
Purchase #5	$160.68	4.839%	$168.4553	$168.46	$168.45	$168.50
Purchase #6	$135.51	10.736%	$150.0584	$150.06	$150.05	$150.10
Purchase #7	$7.39	11.486%	$8.2388	$8.24	$8.25	$8.20
7 purchase totals =	$671.95		$722.9524	$722.96	$722.90	$722.90