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	$144.50	6.765%	$154.2754	$154.28	$154.30	$154.30
Purchase #2	$165.53	6.245%	$175.8673	$175.87	$175.85	$175.90
Purchase #3	$236.55	3.365%	$244.5099	$244.51	$244.50	$244.50
Purchase #4	$139.69	7.852%	$150.6585	$150.66	$150.65	$150.70
Purchase #5	$96.99	3.219%	$100.1121	$100.11	$100.10	$100.10
Purchase #6	$28.96	13.133%	$32.7633	$32.76	$32.75	$32.80
Purchase #7	$174.55	8.537%	$189.4513	$189.45	$189.45	$189.50
7 purchase totals =	$986.77		$1,047.6378	$1,047.64	$1,047.60	$1,047.80