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	$118.98	7.800%	$128.2604	$128.26	$128.25	$128.30
Purchase #2	$139.88	3.258%	$144.4373	$144.44	$144.45	$144.40
Purchase #3	$83.78	11.461%	$93.382	$93.38	$93.40	$93.40
Purchase #4	$109.73	8.229%	$118.7597	$118.76	$118.75	$118.80
Purchase #5	$191.78	3.190%	$197.8978	$197.90	$197.90	$197.90
Purchase #6	$223.94	11.635%	$249.9954	$250.00	$250.00	$250.00
Purchase #7	$12.33	6.507%	$13.1323	$13.13	$13.15	$13.10
7 purchase totals =	$880.42		$945.8649	$945.87	$945.90	$945.90