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	$72.30	5.747%	$76.4551	$76.46	$76.45	$76.50
Purchase #2	$41.25	10.822%	$45.7141	$45.71	$45.70	$45.70
Purchase #3	$167.33	13.578%	$190.0501	$190.05	$190.05	$190.10
Purchase #4	$121.44	7.422%	$130.4533	$130.45	$130.45	$130.50
Purchase #5	$233.50	13.623%	$265.3097	$265.31	$265.30	$265.30
Purchase #6	$243.64	10.368%	$268.9006	$268.90	$268.90	$268.90
Purchase #7	$175.58	5.796%	$185.7566	$185.76	$185.75	$185.80
7 purchase totals =	$1,055.04		$1,162.6395	$1,162.64	$1,162.60	$1,162.80