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	$33.73	7.630%	$36.3036	$36.30	$36.30	$36.30
Purchase #2	$229.44	12.784%	$258.7716	$258.77	$258.75	$258.80
Purchase #3	$35.93	4.451%	$37.5292	$37.53	$37.55	$37.50
Purchase #4	$139.54	11.111%	$155.0443	$155.04	$155.05	$155.00
Purchase #5	$168.56	10.404%	$186.097	$186.10	$186.10	$186.10
Purchase #6	$81.62	4.196%	$85.0448	$85.04	$85.05	$85.00
Purchase #7	$224.61	11.170%	$249.6989	$249.70	$249.70	$249.70
7 purchase totals =	$913.43		$1,008.4894	$1,008.48	$1,008.50	$1,008.40