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	$97.41	4.795%	$102.0808	$102.08	$102.10	$102.10
Purchase #2	$87.46	13.756%	$99.491	$99.49	$99.50	$99.50
Purchase #3	$110.32	13.856%	$125.6059	$125.61	$125.60	$125.60
Purchase #4	$97.72	11.730%	$109.1826	$109.18	$109.20	$109.20
Purchase #5	$111.60	12.406%	$125.4451	$125.45	$125.45	$125.40
Purchase #6	$49.33	11.369%	$54.9383	$54.94	$54.95	$54.90
Purchase #7	$66.44	9.486%	$72.7425	$72.74	$72.75	$72.70
7 purchase totals =	$620.28		$689.4862	$689.49	$689.55	$689.40