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	$16.54	5.437%	$17.4393	$17.44	$17.45	$17.40
Purchase #2	$61.52	5.680%	$65.0143	$65.01	$65.00	$65.00
Purchase #3	$233.45	9.169%	$254.855	$254.86	$254.85	$254.90
Purchase #4	$180.30	13.272%	$204.2294	$204.23	$204.25	$204.20
Purchase #5	$234.56	4.688%	$245.5562	$245.56	$245.55	$245.60
Purchase #6	$222.85	5.679%	$235.5057	$235.51	$235.50	$235.50
Purchase #7	$189.31	3.619%	$196.1611	$196.16	$196.15	$196.20
7 purchase totals =	$1,138.53		$1,218.7610	$1,218.77	$1,218.75	$1,218.80