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	$210.57	5.619%	$222.4019	$222.40	$222.40	$222.40
Purchase #2	$115.56	9.559%	$126.6064	$126.61	$126.60	$126.60
Purchase #3	$58.31	5.644%	$61.601	$61.60	$61.60	$61.60
Purchase #4	$53.37	10.180%	$58.8031	$58.80	$58.80	$58.80
Purchase #5	$201.90	10.805%	$223.7153	$223.72	$223.70	$223.70
Purchase #6	$82.84	3.710%	$85.9134	$85.91	$85.90	$85.90
Purchase #7	$210.47	7.654%	$226.5794	$226.58	$226.60	$226.60
7 purchase totals =	$933.02		$1,005.6205	$1,005.62	$1,005.60	$1,005.60