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	$42.79	9.567%	$46.8837	$46.88	$46.90	$46.90
Purchase #2	$145.61	12.427%	$163.705	$163.71	$163.70	$163.70
Purchase #3	$213.77	3.706%	$221.6923	$221.69	$221.70	$221.70
Purchase #4	$77.42	10.315%	$85.4059	$85.41	$85.40	$85.40
Purchase #5	$197.53	10.753%	$218.7704	$218.77	$218.75	$218.80
Purchase #6	$137.32	10.179%	$151.2978	$151.30	$151.30	$151.30
Purchase #7	$124.79	5.518%	$131.6759	$131.68	$131.70	$131.70
7 purchase totals =	$939.23		$1,019.4310	$1,019.44	$1,019.45	$1,019.50