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	$219.80	3.235%	$226.9105	$226.91	$226.90	$226.90
Purchase #2	$178.67	7.118%	$191.3877	$191.39	$191.40	$191.40
Purchase #3	$103.59	8.870%	$112.7784	$112.78	$112.80	$112.80
Purchase #4	$98.92	10.412%	$109.2196	$109.22	$109.20	$109.20
Purchase #5	$113.58	3.104%	$117.1055	$117.11	$117.10	$117.10
Purchase #6	$114.82	11.383%	$127.89	$127.89	$127.90	$127.90
Purchase #7	$206.92	6.744%	$220.8747	$220.87	$220.85	$220.90
7 purchase totals =	$1,036.30		$1,106.1664	$1,106.17	$1,106.15	$1,106.20