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	$162.42	5.431%	$171.241	$171.24	$171.25	$171.20
Purchase #2	$233.55	4.355%	$243.7211	$243.72	$243.70	$243.70
Purchase #3	$89.42	5.656%	$94.4776	$94.48	$94.50	$94.50
Purchase #4	$71.44	6.141%	$75.8271	$75.83	$75.85	$75.80
Purchase #5	$174.77	3.706%	$181.247	$181.25	$181.25	$181.20
Purchase #6	$25.94	11.298%	$28.8707	$28.87	$28.85	$28.90
Purchase #7	$134.92	8.783%	$146.77	$146.77	$146.75	$146.80
7 purchase totals =	$892.46		$942.1545	$942.16	$942.15	$942.10