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	$204.55	7.432%	$219.7522	$219.75	$219.75	$219.80
Purchase #2	$122.73	3.673%	$127.2379	$127.24	$127.25	$127.20
Purchase #3	$16.49	9.488%	$18.0546	$18.05	$18.05	$18.10
Purchase #4	$187.47	12.492%	$210.8888	$210.89	$210.90	$210.90
Purchase #5	$151.84	5.777%	$160.6118	$160.61	$160.60	$160.60
Purchase #6	$79.31	13.478%	$89.9994	$90.00	$90.00	$90.00
Purchase #7	$88.82	3.481%	$91.9118	$91.91	$91.90	$91.90
7 purchase totals =	$851.21		$918.4565	$918.45	$918.45	$918.50