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	$94.46	9.387%	$103.327	$103.33	$103.35	$103.30
Purchase #2	$37.84	13.815%	$43.0676	$43.07	$43.05	$43.10
Purchase #3	$170.52	7.678%	$183.6125	$183.61	$183.60	$183.60
Purchase #4	$65.63	11.664%	$73.2851	$73.29	$73.30	$73.30
Purchase #5	$211.34	11.869%	$236.4239	$236.42	$236.40	$236.40
Purchase #6	$112.49	13.533%	$127.7133	$127.71	$127.70	$127.70
Purchase #7	$96.50	9.187%	$105.3655	$105.37	$105.35	$105.40
7 purchase totals =	$788.78		$872.7949	$872.80	$872.75	$872.80