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	$103.25	11.290%	$114.9069	$114.91	$114.90	$114.90
Purchase #2	$160.80	8.695%	$174.7816	$174.78	$174.80	$174.80
Purchase #3	$91.57	10.119%	$100.836	$100.84	$100.85	$100.80
Purchase #4	$81.82	11.784%	$91.4617	$91.46	$91.45	$91.50
Purchase #5	$54.87	7.720%	$59.106	$59.11	$59.10	$59.10
Purchase #6	$13.33	6.773%	$14.2328	$14.23	$14.25	$14.20
Purchase #7	$181.71	6.441%	$193.4139	$193.41	$193.40	$193.40
7 purchase totals =	$687.35		$748.7389	$748.74	$748.75	$748.70