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	$105.31	7.632%	$113.3473	$113.35	$113.35	$113.30
Purchase #2	$141.53	3.585%	$146.6039	$146.60	$146.60	$146.60
Purchase #3	$182.46	3.539%	$188.9173	$188.92	$188.90	$188.90
Purchase #4	$90.54	10.272%	$99.8403	$99.84	$99.85	$99.80
Purchase #5	$59.62	12.721%	$67.2043	$67.20	$67.20	$67.20
Purchase #6	$240.61	7.618%	$258.9397	$258.94	$258.95	$258.90
Purchase #7	$228.28	6.456%	$243.0178	$243.02	$243.00	$243.00
7 purchase totals =	$1,048.35		$1,117.8706	$1,117.87	$1,117.85	$1,117.70