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	$74.98	13.741%	$85.283	$85.28	$85.30	$85.30
Purchase #2	$73.37	13.332%	$83.1517	$83.15	$83.15	$83.20
Purchase #3	$233.58	5.648%	$246.7726	$246.77	$246.75	$246.80
Purchase #4	$17.87	5.525%	$18.8573	$18.86	$18.85	$18.90
Purchase #5	$90.44	4.339%	$94.3642	$94.36	$94.35	$94.40
Purchase #6	$182.33	13.219%	$206.4322	$206.43	$206.45	$206.40
Purchase #7	$43.85	3.498%	$45.3839	$45.38	$45.40	$45.40
7 purchase totals =	$716.42		$780.2449	$780.23	$780.25	$780.40