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	$211.97	7.710%	$228.3129	$228.31	$228.30	$228.30
Purchase #2	$51.39	6.343%	$54.6497	$54.65	$54.65	$54.60
Purchase #3	$83.31	3.464%	$86.1959	$86.20	$86.20	$86.20
Purchase #4	$56.40	5.583%	$59.5488	$59.55	$59.55	$59.50
Purchase #5	$75.62	9.621%	$82.8954	$82.90	$82.90	$82.90
Purchase #6	$45.55	3.290%	$47.0486	$47.05	$47.05	$47.00
Purchase #7	$50.79	3.178%	$52.4041	$52.40	$52.40	$52.40
7 purchase totals =	$575.03		$611.0554	$611.06	$611.05	$610.90