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	$247.27	8.600%	$268.5352	$268.54	$268.55	$268.50
Purchase #2	$160.84	3.546%	$166.5434	$166.54	$166.55	$166.50
Purchase #3	$42.44	4.393%	$44.3044	$44.30	$44.30	$44.30
Purchase #4	$130.33	8.823%	$141.829	$141.83	$141.85	$141.80
Purchase #5	$52.86	5.790%	$55.9206	$55.92	$55.90	$55.90
Purchase #6	$212.77	4.436%	$222.2085	$222.21	$222.20	$222.20
Purchase #7	$95.28	7.549%	$102.4727	$102.47	$102.45	$102.50
7 purchase totals =	$941.79		$1,001.8138	$1,001.81	$1,001.80	$1,001.70