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	$198.88	5.790%	$210.3952	$210.40	$210.40	$210.40
Purchase #2	$185.68	8.188%	$200.8835	$200.88	$200.90	$200.90
Purchase #3	$136.27	7.602%	$146.6292	$146.63	$146.65	$146.60
Purchase #4	$57.77	11.751%	$64.5586	$64.56	$64.55	$64.60
Purchase #5	$73.74	12.873%	$83.2326	$83.23	$83.25	$83.20
Purchase #6	$206.53	7.743%	$222.5216	$222.52	$222.50	$222.50
Purchase #7	$122.56	4.136%	$127.6291	$127.63	$127.65	$127.60
7 purchase totals =	$981.43		$1,055.8498	$1,055.85	$1,055.90	$1,055.80