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	$63.30	3.312%	$65.3965	$65.40	$65.40	$65.40
Purchase #2	$171.46	11.539%	$191.2448	$191.24	$191.25	$191.20
Purchase #3	$17.59	11.225%	$19.5645	$19.56	$19.55	$19.60
Purchase #4	$250.45	12.343%	$281.363	$281.36	$281.35	$281.40
Purchase #5	$12.85	4.643%	$13.4466	$13.45	$13.45	$13.40
Purchase #6	$96.77	12.808%	$109.1643	$109.16	$109.15	$109.20
Purchase #7	$197.40	6.745%	$210.7146	$210.71	$210.70	$210.70
7 purchase totals =	$809.82		$890.8943	$890.88	$890.85	$890.90