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	$86.64	5.788%	$91.6547	$91.65	$91.65	$91.70
Purchase #2	$136.46	11.604%	$152.2948	$152.29	$152.30	$152.30
Purchase #3	$61.95	6.630%	$66.0573	$66.06	$66.05	$66.10
Purchase #4	$219.71	6.652%	$234.3251	$234.33	$234.35	$234.30
Purchase #5	$165.75	11.817%	$185.3367	$185.34	$185.35	$185.30
Purchase #6	$96.92	12.415%	$108.9526	$108.95	$108.95	$109.00
Purchase #7	$118.94	7.487%	$127.845	$127.85	$127.85	$127.80
7 purchase totals =	$886.37		$966.4662	$966.47	$966.50	$966.50