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	$99.27	6.317%	$105.5409	$105.54	$105.55	$105.50
Purchase #2	$43.64	4.572%	$45.6352	$45.64	$45.65	$45.60
Purchase #3	$62.28	9.745%	$68.3492	$68.35	$68.35	$68.30
Purchase #4	$53.32	6.493%	$56.7821	$56.78	$56.80	$56.80
Purchase #5	$47.44	11.859%	$53.0659	$53.07	$53.05	$53.10
Purchase #6	$70.62	8.274%	$76.4631	$76.46	$76.45	$76.50
Purchase #7	$134.96	9.123%	$147.2724	$147.27	$147.25	$147.30
7 purchase totals =	$511.53		$553.1088	$553.11	$553.10	$553.10