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	$56.25	12.504%	$63.2835	$63.28	$63.30	$63.30
Purchase #2	$99.54	10.619%	$110.1102	$110.11	$110.10	$110.10
Purchase #3	$28.82	7.856%	$31.0841	$31.08	$31.10	$31.10
Purchase #4	$128.90	10.747%	$142.7529	$142.75	$142.75	$142.80
Purchase #5	$132.34	8.746%	$143.9145	$143.91	$143.90	$143.90
Purchase #6	$73.44	12.363%	$82.5194	$82.52	$82.50	$82.50
Purchase #7	$204.96	3.198%	$211.5146	$211.51	$211.50	$211.50
7 purchase totals =	$724.25		$785.1792	$785.16	$785.15	$785.20