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	$156.72	4.794%	$164.2332	$164.23	$164.25	$164.20
Purchase #2	$89.56	4.483%	$93.575	$93.58	$93.60	$93.60
Purchase #3	$214.28	9.872%	$235.4337	$235.43	$235.45	$235.40
Purchase #4	$189.94	13.127%	$214.8734	$214.87	$214.85	$214.90
Purchase #5	$150.41	9.540%	$164.7591	$164.76	$164.75	$164.80
Purchase #6	$92.54	7.870%	$99.8229	$99.82	$99.80	$99.80
Purchase #7	$118.83	11.469%	$132.4586	$132.46	$132.45	$132.50
7 purchase totals =	$1,012.28		$1,105.1559	$1,105.15	$1,105.15	$1,105.20