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	$157.72	10.192%	$173.7948	$173.79	$173.80	$173.80
Purchase #2	$23.97	13.123%	$27.1156	$27.12	$27.10	$27.10
Purchase #3	$35.76	8.743%	$38.8865	$38.89	$38.90	$38.90
Purchase #4	$69.50	3.563%	$71.9763	$71.98	$72.00	$72.00
Purchase #5	$196.74	6.104%	$208.749	$208.75	$208.75	$208.70
Purchase #6	$136.40	11.324%	$151.8459	$151.85	$151.85	$151.80
Purchase #7	$67.25	4.315%	$70.1518	$70.15	$70.15	$70.20
7 purchase totals =	$687.34		$742.5199	$742.53	$742.55	$742.50