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	$169.28	6.821%	$180.8266	$180.83	$180.85	$180.80
Purchase #2	$142.80	11.859%	$159.7347	$159.73	$159.75	$159.70
Purchase #3	$41.99	4.442%	$43.8552	$43.86	$43.85	$43.90
Purchase #4	$234.89	13.473%	$266.5367	$266.54	$266.55	$266.50
Purchase #5	$11.37	7.369%	$12.2079	$12.21	$12.20	$12.20
Purchase #6	$131.66	8.328%	$142.6246	$142.62	$142.60	$142.60
Purchase #7	$248.98	10.616%	$275.4117	$275.41	$275.40	$275.40
7 purchase totals =	$980.97		$1,081.1974	$1,081.20	$1,081.20	$1,081.10