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	$51.56	4.317%	$53.7858	$53.79	$53.80	$53.80
Purchase #2	$81.53	11.563%	$90.9573	$90.96	$90.95	$91.00
Purchase #3	$54.52	6.437%	$58.0295	$58.03	$58.05	$58.00
Purchase #4	$238.93	13.526%	$271.2477	$271.25	$271.25	$271.20
Purchase #5	$81.29	12.845%	$91.7317	$91.73	$91.75	$91.70
Purchase #6	$93.47	11.587%	$104.3004	$104.30	$104.30	$104.30
Purchase #7	$99.55	12.829%	$112.3213	$112.32	$112.30	$112.30
7 purchase totals =	$700.85		$782.3737	$782.38	$782.40	$782.30