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	$96.96	8.105%	$104.8186	$104.82	$104.80	$104.80
Purchase #2	$16.25	5.746%	$17.1837	$17.18	$17.20	$17.20
Purchase #3	$150.76	13.446%	$171.0312	$171.03	$171.05	$171.00
Purchase #4	$78.66	13.491%	$89.272	$89.27	$89.25	$89.30
Purchase #5	$98.30	7.536%	$105.7079	$105.71	$105.70	$105.70
Purchase #6	$166.36	13.370%	$188.6023	$188.60	$188.60	$188.60
Purchase #7	$99.44	6.335%	$105.7395	$105.74	$105.75	$105.70
7 purchase totals =	$706.73		$782.3552	$782.35	$782.35	$782.30