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	$223.39	7.650%	$240.4793	$240.48	$240.50	$240.50
Purchase #2	$211.73	5.103%	$222.5346	$222.53	$222.55	$222.50
Purchase #3	$67.81	11.306%	$75.4766	$75.48	$75.50	$75.50
Purchase #4	$89.77	11.355%	$99.9634	$99.96	$99.95	$100.00
Purchase #5	$243.84	10.125%	$268.5288	$268.53	$268.55	$268.50
Purchase #6	$171.55	4.572%	$179.3933	$179.39	$179.40	$179.40
Purchase #7	$80.50	4.147%	$83.8383	$83.84	$83.85	$83.80
7 purchase totals =	$1,088.59		$1,170.2143	$1,170.21	$1,170.30	$1,170.20