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	$232.61	3.740%	$241.3096	$241.31	$241.30	$241.30
Purchase #2	$81.78	9.277%	$89.3667	$89.37	$89.35	$89.40
Purchase #3	$176.52	8.464%	$191.4607	$191.46	$191.45	$191.50
Purchase #4	$126.42	11.391%	$140.8205	$140.82	$140.80	$140.80
Purchase #5	$195.87	8.222%	$211.9744	$211.97	$211.95	$212.00
Purchase #6	$58.55	4.546%	$61.2117	$61.21	$61.20	$61.20
Purchase #7	$219.31	8.638%	$238.254	$238.25	$238.25	$238.30
7 purchase totals =	$1,091.06		$1,174.3976	$1,174.39	$1,174.30	$1,174.50