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	$89.38	12.557%	$100.6034	$100.60	$100.60	$100.60
Purchase #2	$146.96	3.250%	$151.7362	$151.74	$151.75	$151.70
Purchase #3	$43.41	6.293%	$46.1418	$46.14	$46.15	$46.10
Purchase #4	$75.73	9.384%	$82.8365	$82.84	$82.85	$82.80
Purchase #5	$164.86	6.313%	$175.2676	$175.27	$175.25	$175.30
Purchase #6	$231.31	7.610%	$248.9127	$248.91	$248.90	$248.90
Purchase #7	$156.60	7.809%	$168.8289	$168.83	$168.85	$168.80
7 purchase totals =	$908.25		$974.3271	$974.33	$974.35	$974.20