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	$164.30	10.542%	$181.6205	$181.62	$181.60	$181.60
Purchase #2	$61.42	13.593%	$69.7688	$69.77	$69.75	$69.80
Purchase #3	$169.73	7.353%	$182.2102	$182.21	$182.20	$182.20
Purchase #4	$73.37	13.802%	$83.4965	$83.50	$83.50	$83.50
Purchase #5	$211.67	4.461%	$221.1126	$221.11	$221.10	$221.10
Purchase #6	$90.38	10.304%	$99.6928	$99.69	$99.70	$99.70
Purchase #7	$186.44	12.285%	$209.3442	$209.34	$209.35	$209.30
7 purchase totals =	$957.31		$1,047.2456	$1,047.24	$1,047.20	$1,047.20