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	$139.54	5.745%	$147.5566	$147.56	$147.55	$147.60
Purchase #2	$31.41	3.261%	$32.4343	$32.43	$32.45	$32.40
Purchase #3	$235.57	13.829%	$268.147	$268.15	$268.15	$268.10
Purchase #4	$117.76	4.490%	$123.0474	$123.05	$123.05	$123.00
Purchase #5	$73.84	6.399%	$78.565	$78.57	$78.55	$78.60
Purchase #6	$28.52	3.659%	$29.5635	$29.56	$29.55	$29.60
Purchase #7	$84.30	10.206%	$92.9037	$92.90	$92.90	$92.90
7 purchase totals =	$710.94		$772.2175	$772.22	$772.20	$772.20