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	$197.73	8.834%	$215.1975	$215.20	$215.20	$215.20
Purchase #2	$41.38	9.314%	$45.2341	$45.23	$45.25	$45.20
Purchase #3	$218.95	6.364%	$232.884	$232.88	$232.90	$232.90
Purchase #4	$137.65	10.608%	$152.2519	$152.25	$152.25	$152.30
Purchase #5	$147.84	8.497%	$160.402	$160.40	$160.40	$160.40
Purchase #6	$108.70	13.840%	$123.7441	$123.74	$123.75	$123.70
Purchase #7	$151.82	12.269%	$170.4468	$170.45	$170.45	$170.40
7 purchase totals =	$1,004.07		$1,100.1604	$1,100.15	$1,100.20	$1,100.10