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	$63.60	13.296%	$72.0563	$72.06	$72.05	$72.10
Purchase #2	$187.71	8.400%	$203.4776	$203.48	$203.50	$203.50
Purchase #3	$223.66	4.199%	$233.0515	$233.05	$233.05	$233.10
Purchase #4	$171.90	4.848%	$180.2337	$180.23	$180.25	$180.20
Purchase #5	$85.75	6.397%	$91.2354	$91.24	$91.25	$91.20
Purchase #6	$27.93	12.731%	$31.4858	$31.49	$31.50	$31.50
Purchase #7	$191.31	11.610%	$213.5211	$213.52	$213.50	$213.50
7 purchase totals =	$951.86		$1,025.0614	$1,025.07	$1,025.10	$1,025.10