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	$163.46	11.864%	$182.8529	$182.85	$182.85	$182.90
Purchase #2	$67.81	12.696%	$76.4192	$76.42	$76.40	$76.40
Purchase #3	$138.73	6.652%	$147.9583	$147.96	$147.95	$148.00
Purchase #4	$119.88	6.213%	$127.3281	$127.33	$127.35	$127.30
Purchase #5	$154.54	6.221%	$164.1539	$164.15	$164.15	$164.20
Purchase #6	$169.73	11.112%	$188.5904	$188.59	$188.60	$188.60
Purchase #7	$58.62	7.177%	$62.8272	$62.83	$62.85	$62.80
7 purchase totals =	$872.77		$950.1300	$950.13	$950.15	$950.20