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	$14.80	6.309%	$15.7337	$15.73	$15.75	$15.70
Purchase #2	$46.36	12.166%	$52.0002	$52.00	$52.00	$52.00
Purchase #3	$167.34	10.845%	$185.488	$185.49	$185.50	$185.50
Purchase #4	$17.46	7.867%	$18.8336	$18.83	$18.85	$18.80
Purchase #5	$21.42	13.564%	$24.3254	$24.33	$24.35	$24.30
Purchase #6	$42.44	7.669%	$45.6947	$45.69	$45.70	$45.70
Purchase #7	$65.64	8.337%	$71.1124	$71.11	$71.10	$71.10
7 purchase totals =	$375.46		$413.1880	$413.18	$413.25	$413.10