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	$175.96	8.181%	$190.3553	$190.36	$190.35	$190.40
Purchase #2	$118.99	7.139%	$127.4847	$127.48	$127.50	$127.50
Purchase #3	$89.44	8.797%	$97.308	$97.31	$97.30	$97.30
Purchase #4	$228.42	13.568%	$259.412	$259.41	$259.40	$259.40
Purchase #5	$205.65	6.868%	$219.774	$219.77	$219.75	$219.80
Purchase #6	$35.53	9.213%	$38.8034	$38.80	$38.80	$38.80
Purchase #7	$123.89	13.102%	$140.1221	$140.12	$140.10	$140.10
7 purchase totals =	$977.88		$1,073.2595	$1,073.25	$1,073.20	$1,073.30