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	$156.96	3.396%	$162.2904	$162.29	$162.30	$162.30
Purchase #2	$108.49	3.196%	$111.9573	$111.96	$111.95	$112.00
Purchase #3	$26.76	4.292%	$27.9085	$27.91	$27.90	$27.90
Purchase #4	$248.78	6.233%	$264.2865	$264.29	$264.30	$264.30
Purchase #5	$240.41	7.477%	$258.3855	$258.39	$258.40	$258.40
Purchase #6	$175.70	9.794%	$192.9081	$192.91	$192.90	$192.90
Purchase #7	$190.35	8.459%	$206.4517	$206.45	$206.45	$206.50
7 purchase totals =	$1,147.45		$1,224.1880	$1,224.20	$1,224.20	$1,224.30