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	$30.74	4.728%	$32.1934	$32.19	$32.20	$32.20
Purchase #2	$38.91	7.470%	$41.8166	$41.82	$41.80	$41.80
Purchase #3	$27.94	5.414%	$29.4527	$29.45	$29.45	$29.50
Purchase #4	$142.86	6.544%	$152.2088	$152.21	$152.20	$152.20
Purchase #5	$131.62	12.755%	$148.4081	$148.41	$148.40	$148.40
Purchase #6	$104.26	4.555%	$109.009	$109.01	$109.00	$109.00
Purchase #7	$187.45	13.335%	$212.4465	$212.45	$212.45	$212.40
7 purchase totals =	$663.78		$725.5351	$725.54	$725.50	$725.50