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	$241.43	9.408%	$264.1437	$264.14	$264.15	$264.10
Purchase #2	$154.86	13.229%	$175.3464	$175.35	$175.35	$175.30
Purchase #3	$162.31	3.241%	$167.5705	$167.57	$167.55	$167.60
Purchase #4	$243.41	3.675%	$252.3553	$252.36	$252.35	$252.40
Purchase #5	$154.60	9.660%	$169.5344	$169.53	$169.55	$169.50
Purchase #6	$78.75	6.572%	$83.9255	$83.93	$83.95	$83.90
Purchase #7	$73.39	7.459%	$78.8642	$78.86	$78.85	$78.90
7 purchase totals =	$1,108.75		$1,191.7400	$1,191.74	$1,191.75	$1,191.70