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	$135.89	9.787%	$149.1896	$149.19	$149.20	$149.20
Purchase #2	$215.33	12.543%	$242.3388	$242.34	$242.35	$242.30
Purchase #3	$88.48	13.598%	$100.5115	$100.51	$100.50	$100.50
Purchase #4	$223.81	11.595%	$249.7608	$249.76	$249.75	$249.80
Purchase #5	$93.42	3.304%	$96.5066	$96.51	$96.50	$96.50
Purchase #6	$98.32	7.400%	$105.5957	$105.60	$105.60	$105.60
Purchase #7	$168.60	7.379%	$181.041	$181.04	$181.05	$181.00
7 purchase totals =	$1,023.85		$1,124.9440	$1,124.95	$1,124.95	$1,124.90