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	$162.97	3.269%	$168.2975	$168.30	$168.30	$168.30
Purchase #2	$73.69	12.511%	$82.9094	$82.91	$82.90	$82.90
Purchase #3	$129.73	13.631%	$147.4135	$147.41	$147.40	$147.40
Purchase #4	$217.37	8.345%	$235.5095	$235.51	$235.50	$235.50
Purchase #5	$89.66	6.468%	$95.4592	$95.46	$95.45	$95.50
Purchase #6	$90.55	4.719%	$94.8231	$94.82	$94.80	$94.80
Purchase #7	$205.40	4.389%	$214.415	$214.42	$214.40	$214.40
7 purchase totals =	$969.37		$1,038.8272	$1,038.83	$1,038.75	$1,038.80