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	$57.85	7.349%	$62.1014	$62.10	$62.10	$62.10
Purchase #2	$114.55	10.588%	$126.6786	$126.68	$126.70	$126.70
Purchase #3	$112.47	4.312%	$117.3197	$117.32	$117.30	$117.30
Purchase #4	$162.52	13.708%	$184.7982	$184.80	$184.80	$184.80
Purchase #5	$113.98	10.845%	$126.3411	$126.34	$126.35	$126.30
Purchase #6	$178.55	12.516%	$200.8973	$200.90	$200.90	$200.90
Purchase #7	$217.41	11.850%	$243.1731	$243.17	$243.15	$243.20
7 purchase totals =	$957.33		$1,061.3094	$1,061.31	$1,061.30	$1,061.30