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	$86.54	4.173%	$90.1513	$90.15	$90.15	$90.20
Purchase #2	$175.92	6.414%	$187.2035	$187.20	$187.20	$187.20
Purchase #3	$11.28	5.377%	$11.8865	$11.89	$11.90	$11.90
Purchase #4	$56.66	3.860%	$58.8471	$58.85	$58.85	$58.80
Purchase #5	$28.55	13.594%	$32.4311	$32.43	$32.45	$32.40
Purchase #6	$239.52	11.118%	$266.1498	$266.15	$266.15	$266.10
Purchase #7	$54.31	4.143%	$56.5601	$56.56	$56.55	$56.60
7 purchase totals =	$652.78		$703.2294	$703.23	$703.25	$703.20