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	$144.54	5.731%	$152.8236	$152.82	$152.80	$152.80
Purchase #2	$41.61	13.511%	$47.2319	$47.23	$47.25	$47.20
Purchase #3	$178.66	12.405%	$200.8228	$200.82	$200.80	$200.80
Purchase #4	$33.46	7.142%	$35.8497	$35.85	$35.85	$35.80
Purchase #5	$235.61	6.836%	$251.7163	$251.72	$251.70	$251.70
Purchase #6	$178.42	8.124%	$192.9148	$192.91	$192.90	$192.90
Purchase #7	$175.66	4.478%	$183.5261	$183.53	$183.55	$183.50
7 purchase totals =	$987.96		$1,064.8852	$1,064.88	$1,064.85	$1,064.70