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	$197.33	3.769%	$204.7674	$204.77	$204.75	$204.80
Purchase #2	$82.86	10.859%	$91.8578	$91.86	$91.85	$91.90
Purchase #3	$120.71	13.312%	$136.7789	$136.78	$136.80	$136.80
Purchase #4	$32.72	3.691%	$33.9277	$33.93	$33.95	$33.90
Purchase #5	$162.92	11.810%	$182.1609	$182.16	$182.15	$182.20
Purchase #6	$39.51	8.728%	$42.9584	$42.96	$42.95	$43.00
Purchase #7	$45.29	12.304%	$50.8625	$50.86	$50.85	$50.90
7 purchase totals =	$681.34		$743.3136	$743.32	$743.30	$743.50