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	$190.59	9.506%	$208.7075	$208.71	$208.70	$208.70
Purchase #2	$201.32	10.450%	$222.3579	$222.36	$222.35	$222.40
Purchase #3	$126.55	5.190%	$133.1179	$133.12	$133.10	$133.10
Purchase #4	$111.95	9.471%	$122.5528	$122.55	$122.55	$122.60
Purchase #5	$98.81	5.791%	$104.5321	$104.53	$104.55	$104.50
Purchase #6	$77.54	10.558%	$85.7267	$85.73	$85.75	$85.70
Purchase #7	$130.33	8.539%	$141.4589	$141.46	$141.45	$141.50
7 purchase totals =	$937.09		$1,018.4538	$1,018.46	$1,018.45	$1,018.50