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	$129.72	11.807%	$145.036	$145.04	$145.05	$145.00
Purchase #2	$208.30	7.222%	$223.3434	$223.34	$223.35	$223.30
Purchase #3	$60.71	3.513%	$62.8427	$62.84	$62.85	$62.80
Purchase #4	$134.36	3.432%	$138.9712	$138.97	$138.95	$139.00
Purchase #5	$109.78	12.844%	$123.8801	$123.88	$123.90	$123.90
Purchase #6	$41.89	11.343%	$46.6416	$46.64	$46.65	$46.60
Purchase #7	$114.61	11.454%	$127.7374	$127.74	$127.75	$127.70
7 purchase totals =	$799.37		$868.4524	$868.45	$868.50	$868.30