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	$192.83	7.618%	$207.5198	$207.52	$207.50	$207.50
Purchase #2	$33.52	11.197%	$37.2732	$37.27	$37.25	$37.30
Purchase #3	$227.40	6.786%	$242.8314	$242.83	$242.85	$242.80
Purchase #4	$245.73	5.825%	$260.0438	$260.04	$260.05	$260.00
Purchase #5	$83.90	6.405%	$89.2738	$89.27	$89.25	$89.30
Purchase #6	$188.29	9.340%	$205.8763	$205.88	$205.90	$205.90
Purchase #7	$203.27	13.857%	$231.4371	$231.44	$231.45	$231.40
7 purchase totals =	$1,174.94		$1,274.2554	$1,274.25	$1,274.25	$1,274.20