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	$91.72	7.562%	$98.6559	$98.66	$98.65	$98.70
Purchase #2	$176.80	6.402%	$188.1187	$188.12	$188.10	$188.10
Purchase #3	$245.93	9.631%	$269.6155	$269.62	$269.60	$269.60
Purchase #4	$56.56	9.550%	$61.9615	$61.96	$61.95	$62.00
Purchase #5	$139.91	8.326%	$151.5589	$151.56	$151.55	$151.60
Purchase #6	$81.89	4.256%	$85.3752	$85.38	$85.40	$85.40
Purchase #7	$9.92	13.602%	$11.2693	$11.27	$11.25	$11.30
7 purchase totals =	$802.73		$866.5550	$866.57	$866.50	$866.70