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	$203.73	4.237%	$212.362	$212.36	$212.35	$212.40
Purchase #2	$177.33	7.793%	$191.1493	$191.15	$191.15	$191.10
Purchase #3	$62.60	11.828%	$70.0043	$70.00	$70.00	$70.00
Purchase #4	$202.30	6.511%	$215.4718	$215.47	$215.45	$215.50
Purchase #5	$205.69	11.547%	$229.441	$229.44	$229.45	$229.40
Purchase #6	$103.26	10.659%	$114.2665	$114.27	$114.25	$114.30
Purchase #7	$89.98	9.407%	$98.4444	$98.44	$98.45	$98.40
7 purchase totals =	$1,044.89		$1,131.1393	$1,131.13	$1,131.10	$1,131.10