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	$47.57	10.826%	$52.7199	$52.72	$52.70	$52.70
Purchase #2	$235.98	3.814%	$244.9803	$244.98	$245.00	$245.00
Purchase #3	$184.92	5.236%	$194.6024	$194.60	$194.60	$194.60
Purchase #4	$248.64	13.575%	$282.3929	$282.39	$282.40	$282.40
Purchase #5	$199.97	6.325%	$212.6181	$212.62	$212.60	$212.60
Purchase #6	$133.72	13.871%	$152.2683	$152.27	$152.25	$152.30
Purchase #7	$94.71	11.360%	$105.4691	$105.47	$105.45	$105.50
7 purchase totals =	$1,145.51		$1,245.0510	$1,245.05	$1,245.00	$1,245.10