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	$190.30	3.313%	$196.6046	$196.60	$196.60	$196.60
Purchase #2	$150.54	6.840%	$160.8369	$160.84	$160.85	$160.80
Purchase #3	$145.97	5.152%	$153.4904	$153.49	$153.50	$153.50
Purchase #4	$98.98	5.697%	$104.6189	$104.62	$104.60	$104.60
Purchase #5	$203.62	4.795%	$213.3836	$213.38	$213.40	$213.40
Purchase #6	$70.35	11.671%	$78.5605	$78.56	$78.55	$78.60
Purchase #7	$92.30	11.346%	$102.7724	$102.77	$102.75	$102.80
7 purchase totals =	$952.06		$1,010.2673	$1,010.26	$1,010.25	$1,010.30