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	$243.30	8.254%	$263.382	$263.38	$263.40	$263.40
Purchase #2	$95.54	6.374%	$101.6297	$101.63	$101.65	$101.60
Purchase #3	$80.25	6.397%	$85.3836	$85.38	$85.40	$85.40
Purchase #4	$195.34	6.253%	$207.5546	$207.55	$207.55	$207.60
Purchase #5	$100.73	10.730%	$111.5383	$111.54	$111.55	$111.50
Purchase #6	$187.78	3.429%	$194.219	$194.22	$194.20	$194.20
Purchase #7	$211.67	4.365%	$220.9094	$220.91	$220.90	$220.90
7 purchase totals =	$1,114.61		$1,184.6166	$1,184.61	$1,184.65	$1,184.60