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	$147.87	5.691%	$156.2853	$156.29	$156.30	$156.30
Purchase #2	$118.56	10.208%	$130.6626	$130.66	$130.65	$130.70
Purchase #3	$160.45	8.509%	$174.1027	$174.10	$174.10	$174.10
Purchase #4	$53.86	10.354%	$59.4367	$59.44	$59.45	$59.40
Purchase #5	$167.64	4.744%	$175.5928	$175.59	$175.60	$175.60
Purchase #6	$29.60	11.562%	$33.0224	$33.02	$33.00	$33.00
Purchase #7	$22.66	11.110%	$25.1775	$25.18	$25.20	$25.20
7 purchase totals =	$700.64		$754.2800	$754.28	$754.30	$754.30