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	$37.98	5.865%	$40.2075	$40.21	$40.20	$40.20
Purchase #2	$55.91	8.231%	$60.512	$60.51	$60.50	$60.50
Purchase #3	$238.93	6.487%	$254.4294	$254.43	$254.45	$254.40
Purchase #4	$229.68	10.814%	$254.5176	$254.52	$254.50	$254.50
Purchase #5	$225.47	6.800%	$240.802	$240.80	$240.80	$240.80
Purchase #6	$88.63	9.317%	$96.8877	$96.89	$96.90	$96.90
Purchase #7	$95.96	4.864%	$100.6275	$100.63	$100.65	$100.60
7 purchase totals =	$972.56		$1,047.9837	$1,047.99	$1,048.00	$1,047.90