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	$20.66	4.655%	$21.6217	$21.62	$21.60	$21.60
Purchase #2	$80.74	6.674%	$86.1286	$86.13	$86.15	$86.10
Purchase #3	$113.89	3.663%	$118.0618	$118.06	$118.05	$118.10
Purchase #4	$20.94	8.783%	$22.7792	$22.78	$22.80	$22.80
Purchase #5	$83.91	11.862%	$93.8634	$93.86	$93.85	$93.90
Purchase #6	$51.88	3.564%	$53.729	$53.73	$53.75	$53.70
Purchase #7	$47.32	3.363%	$48.9114	$48.91	$48.90	$48.90
7 purchase totals =	$419.34		$445.0951	$445.09	$445.10	$445.10