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	$98.39	6.723%	$105.0048	$105.00	$105.00	$105.00
Purchase #2	$54.46	8.764%	$59.2329	$59.23	$59.25	$59.20
Purchase #3	$27.84	13.109%	$31.4895	$31.49	$31.50	$31.50
Purchase #4	$84.53	7.853%	$91.1681	$91.17	$91.15	$91.20
Purchase #5	$24.36	4.179%	$25.378	$25.38	$25.40	$25.40
Purchase #6	$178.78	5.302%	$188.2589	$188.26	$188.25	$188.30
Purchase #7	$40.61	11.254%	$45.1802	$45.18	$45.20	$45.20
7 purchase totals =	$508.97		$545.7124	$545.71	$545.75	$545.80