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	$117.95	7.689%	$127.0192	$127.02	$127.00	$127.00
Purchase #2	$37.56	13.585%	$42.6625	$42.66	$42.65	$42.70
Purchase #3	$220.87	13.244%	$250.122	$250.12	$250.10	$250.10
Purchase #4	$6.73	11.834%	$7.5264	$7.53	$7.55	$7.50
Purchase #5	$220.50	8.436%	$239.1014	$239.10	$239.10	$239.10
Purchase #6	$185.74	11.384%	$206.8846	$206.88	$206.90	$206.90
Purchase #7	$165.48	7.601%	$178.0581	$178.06	$178.05	$178.10
7 purchase totals =	$954.83		$1,051.3742	$1,051.37	$1,051.35	$1,051.40