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	$148.34	9.246%	$162.0555	$162.06	$162.05	$162.10
Purchase #2	$39.29	7.378%	$42.1888	$42.19	$42.20	$42.20
Purchase #3	$200.62	4.709%	$210.0672	$210.07	$210.05	$210.10
Purchase #4	$113.91	8.223%	$123.2768	$123.28	$123.30	$123.30
Purchase #5	$123.88	3.777%	$128.5589	$128.56	$128.55	$128.60
Purchase #6	$48.78	7.632%	$52.5029	$52.50	$52.50	$52.50
Purchase #7	$189.39	3.166%	$195.3861	$195.39	$195.40	$195.40
7 purchase totals =	$864.21		$914.0362	$914.05	$914.05	$914.20