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	$227.40	4.702%	$238.0923	$238.09	$238.10	$238.10
Purchase #2	$40.50	4.785%	$42.4379	$42.44	$42.45	$42.40
Purchase #3	$122.29	4.120%	$127.3283	$127.33	$127.35	$127.30
Purchase #4	$69.57	9.304%	$76.0428	$76.04	$76.05	$76.00
Purchase #5	$229.48	10.516%	$253.6121	$253.61	$253.60	$253.60
Purchase #6	$170.55	6.635%	$181.866	$181.87	$181.85	$181.90
Purchase #7	$206.74	10.376%	$228.1913	$228.19	$228.20	$228.20
7 purchase totals =	$1,066.53		$1,147.5707	$1,147.57	$1,147.60	$1,147.50