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	$110.71	11.479%	$123.4184	$123.42	$123.40	$123.40
Purchase #2	$26.31	4.846%	$27.585	$27.59	$27.60	$27.60
Purchase #3	$93.30	12.669%	$105.1202	$105.12	$105.10	$105.10
Purchase #4	$131.60	5.663%	$139.0525	$139.05	$139.05	$139.10
Purchase #5	$228.64	11.224%	$254.3026	$254.30	$254.30	$254.30
Purchase #6	$66.52	8.308%	$72.0465	$72.05	$72.05	$72.00
Purchase #7	$40.56	4.508%	$42.3884	$42.39	$42.40	$42.40
7 purchase totals =	$697.64		$763.9136	$763.92	$763.90	$763.90