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	$31.63	11.570%	$35.2896	$35.29	$35.30	$35.30
Purchase #2	$194.65	11.692%	$217.4085	$217.41	$217.40	$217.40
Purchase #3	$127.78	4.828%	$133.9492	$133.95	$133.95	$133.90
Purchase #4	$97.65	11.635%	$109.0116	$109.01	$109.00	$109.00
Purchase #5	$129.91	9.797%	$142.6373	$142.64	$142.65	$142.60
Purchase #6	$95.67	4.244%	$99.7302	$99.73	$99.75	$99.70
Purchase #7	$145.71	7.411%	$156.5086	$156.51	$156.50	$156.50
7 purchase totals =	$823.00		$894.5350	$894.54	$894.55	$894.40