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	$239.52	6.547%	$255.2014	$255.20	$255.20	$255.20
Purchase #2	$95.68	4.125%	$99.6268	$99.63	$99.65	$99.60
Purchase #3	$105.30	3.575%	$109.0645	$109.06	$109.05	$109.10
Purchase #4	$159.76	4.549%	$167.0275	$167.03	$167.05	$167.00
Purchase #5	$204.63	5.511%	$215.9072	$215.91	$215.90	$215.90
Purchase #6	$126.68	13.125%	$143.3068	$143.31	$143.30	$143.30
Purchase #7	$156.73	11.801%	$175.2257	$175.23	$175.25	$175.20
7 purchase totals =	$1,088.30		$1,165.3599	$1,165.37	$1,165.40	$1,165.30