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	$48.61	5.215%	$51.145	$51.15	$51.15	$51.10
Purchase #2	$166.56	9.477%	$182.3449	$182.34	$182.35	$182.30
Purchase #3	$52.43	9.285%	$57.2981	$57.30	$57.30	$57.30
Purchase #4	$50.34	6.837%	$53.7817	$53.78	$53.80	$53.80
Purchase #5	$101.35	7.282%	$108.7303	$108.73	$108.75	$108.70
Purchase #6	$83.62	3.505%	$86.5509	$86.55	$86.55	$86.60
Purchase #7	$175.52	8.431%	$190.3181	$190.32	$190.30	$190.30
7 purchase totals =	$678.43		$730.1690	$730.17	$730.20	$730.10