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	$246.46	6.831%	$263.2957	$263.30	$263.30	$263.30
Purchase #2	$168.51	10.516%	$186.2305	$186.23	$186.25	$186.20
Purchase #3	$56.30	5.468%	$59.3785	$59.38	$59.40	$59.40
Purchase #4	$60.65	4.150%	$63.167	$63.17	$63.15	$63.20
Purchase #5	$74.64	9.780%	$81.9398	$81.94	$81.95	$81.90
Purchase #6	$99.27	10.652%	$109.8442	$109.84	$109.85	$109.80
Purchase #7	$180.71	5.852%	$191.2851	$191.29	$191.30	$191.30
7 purchase totals =	$886.54		$955.1408	$955.15	$955.20	$955.10