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	$144.44	4.499%	$150.9384	$150.94	$150.95	$150.90
Purchase #2	$68.45	7.343%	$73.4763	$73.48	$73.50	$73.50
Purchase #3	$41.92	8.609%	$45.5289	$45.53	$45.55	$45.50
Purchase #4	$28.70	8.827%	$31.2333	$31.23	$31.25	$31.20
Purchase #5	$127.71	12.568%	$143.7606	$143.76	$143.75	$143.80
Purchase #6	$247.81	11.326%	$275.877	$275.88	$275.90	$275.90
Purchase #7	$37.32	5.696%	$39.4457	$39.45	$39.45	$39.40
7 purchase totals =	$696.35		$760.2602	$760.27	$760.35	$760.20