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	$175.92	4.216%	$183.3368	$183.34	$183.35	$183.30
Purchase #2	$41.89	3.322%	$43.2816	$43.28	$43.30	$43.30
Purchase #3	$110.44	12.148%	$123.8563	$123.86	$123.85	$123.90
Purchase #4	$41.36	9.714%	$45.3777	$45.38	$45.40	$45.40
Purchase #5	$49.42	3.331%	$51.0662	$51.07	$51.05	$51.10
Purchase #6	$222.74	3.238%	$229.9523	$229.95	$229.95	$230.00
Purchase #7	$146.32	6.763%	$156.2156	$156.22	$156.20	$156.20
7 purchase totals =	$788.09		$833.0865	$833.10	$833.10	$833.20