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	$93.37	4.773%	$97.8266	$97.83	$97.85	$97.80
Purchase #2	$98.93	12.575%	$111.3704	$111.37	$111.35	$111.40
Purchase #3	$105.93	12.694%	$119.3768	$119.38	$119.40	$119.40
Purchase #4	$120.28	11.221%	$133.7766	$133.78	$133.80	$133.80
Purchase #5	$232.39	8.402%	$251.9154	$251.92	$251.90	$251.90
Purchase #6	$63.50	11.446%	$70.7682	$70.77	$70.75	$70.80
Purchase #7	$98.87	12.593%	$111.3207	$111.32	$111.30	$111.30
7 purchase totals =	$813.27		$896.3547	$896.37	$896.35	$896.40