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	$114.54	4.260%	$119.4194	$119.42	$119.40	$119.40
Purchase #2	$54.68	4.684%	$57.2412	$57.24	$57.25	$57.20
Purchase #3	$71.44	10.347%	$78.8319	$78.83	$78.85	$78.80
Purchase #4	$106.76	5.444%	$112.572	$112.57	$112.55	$112.60
Purchase #5	$234.31	3.162%	$241.7189	$241.72	$241.70	$241.70
Purchase #6	$77.88	6.611%	$83.0286	$83.03	$83.05	$83.00
Purchase #7	$88.75	12.278%	$99.6467	$99.65	$99.65	$99.60
7 purchase totals =	$748.36		$792.4587	$792.46	$792.45	$792.30