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	$70.33	8.119%	$76.0401	$76.04	$76.05	$76.00
Purchase #2	$40.50	11.261%	$45.0607	$45.06	$45.05	$45.10
Purchase #3	$181.56	9.560%	$198.9171	$198.92	$198.90	$198.90
Purchase #4	$109.53	13.814%	$124.6605	$124.66	$124.65	$124.70
Purchase #5	$172.32	4.663%	$180.3553	$180.36	$180.35	$180.40
Purchase #6	$75.55	13.206%	$85.5271	$85.53	$85.55	$85.50
Purchase #7	$60.55	7.420%	$65.0428	$65.04	$65.05	$65.00
7 purchase totals =	$710.34		$775.6036	$775.61	$775.60	$775.60