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	$86.77	10.861%	$96.1941	$96.19	$96.20	$96.20
Purchase #2	$150.32	11.751%	$167.9841	$167.98	$168.00	$168.00
Purchase #3	$134.31	13.847%	$152.9079	$152.91	$152.90	$152.90
Purchase #4	$133.70	4.873%	$140.2152	$140.22	$140.20	$140.20
Purchase #5	$161.81	3.782%	$167.9297	$167.93	$167.95	$167.90
Purchase #6	$190.54	10.156%	$209.8912	$209.89	$209.90	$209.90
Purchase #7	$101.27	7.580%	$108.9463	$108.95	$108.95	$108.90
7 purchase totals =	$958.72		$1,044.0685	$1,044.07	$1,044.10	$1,044.00