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	$191.59	8.156%	$207.2161	$207.22	$207.20	$207.20
Purchase #2	$207.66	6.111%	$220.3501	$220.35	$220.35	$220.40
Purchase #3	$245.50	6.469%	$261.3814	$261.38	$261.40	$261.40
Purchase #4	$161.86	8.153%	$175.0564	$175.06	$175.05	$175.10
Purchase #5	$37.90	11.672%	$42.3237	$42.32	$42.30	$42.30
Purchase #6	$131.92	11.857%	$147.5618	$147.56	$147.55	$147.60
Purchase #7	$140.73	4.117%	$146.5239	$146.52	$146.50	$146.50
7 purchase totals =	$1,117.16		$1,200.4134	$1,200.41	$1,200.35	$1,200.50