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	$118.37	4.761%	$124.0056	$124.01	$124.00	$124.00
Purchase #2	$18.87	4.178%	$19.6584	$19.66	$19.65	$19.70
Purchase #3	$141.33	4.192%	$147.2546	$147.25	$147.25	$147.30
Purchase #4	$243.25	10.406%	$268.5626	$268.56	$268.55	$268.60
Purchase #5	$103.42	7.606%	$111.2861	$111.29	$111.30	$111.30
Purchase #6	$209.43	13.796%	$238.323	$238.32	$238.30	$238.30
Purchase #7	$24.87	9.187%	$27.1548	$27.15	$27.15	$27.20
7 purchase totals =	$859.54		$936.2451	$936.24	$936.20	$936.40