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	$144.64	4.497%	$151.1445	$151.14	$151.15	$151.10
Purchase #2	$45.31	9.711%	$49.7101	$49.71	$49.70	$49.70
Purchase #3	$27.32	3.791%	$28.3557	$28.36	$28.35	$28.40
Purchase #4	$231.33	6.362%	$246.0472	$246.05	$246.05	$246.00
Purchase #5	$99.96	9.189%	$109.1453	$109.15	$109.15	$109.10
Purchase #6	$54.37	12.677%	$61.2625	$61.26	$61.25	$61.30
Purchase #7	$160.88	11.839%	$179.9266	$179.93	$179.95	$179.90
7 purchase totals =	$763.81		$825.5919	$825.60	$825.60	$825.50