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	$196.46	13.446%	$222.876	$222.88	$222.90	$222.90
Purchase #2	$62.34	8.457%	$67.6121	$67.61	$67.60	$67.60
Purchase #3	$127.49	6.815%	$136.1784	$136.18	$136.20	$136.20
Purchase #4	$25.77	4.826%	$27.0137	$27.01	$27.00	$27.00
Purchase #5	$233.96	13.228%	$264.9082	$264.91	$264.90	$264.90
Purchase #6	$172.56	3.260%	$178.1855	$178.19	$178.20	$178.20
Purchase #7	$49.60	7.446%	$53.2932	$53.29	$53.30	$53.30
7 purchase totals =	$868.18		$950.0671	$950.07	$950.10	$950.10