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	$42.98	8.468%	$46.6195	$46.62	$46.60	$46.60
Purchase #2	$182.92	6.529%	$194.8628	$194.86	$194.85	$194.90
Purchase #3	$27.92	6.589%	$29.7596	$29.76	$29.75	$29.80
Purchase #4	$134.52	7.430%	$144.5148	$144.51	$144.50	$144.50
Purchase #5	$12.74	9.587%	$13.9614	$13.96	$13.95	$14.00
Purchase #6	$189.38	3.641%	$196.2753	$196.28	$196.30	$196.30
Purchase #7	$175.91	5.319%	$185.2667	$185.27	$185.25	$185.30
7 purchase totals =	$766.37		$811.2601	$811.26	$811.20	$811.40