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	$198.92	11.203%	$221.205	$221.21	$221.20	$221.20
Purchase #2	$118.86	7.229%	$127.4524	$127.45	$127.45	$127.50
Purchase #3	$185.46	11.394%	$206.5913	$206.59	$206.60	$206.60
Purchase #4	$116.36	11.394%	$129.6181	$129.62	$129.60	$129.60
Purchase #5	$11.59	7.849%	$12.4997	$12.50	$12.50	$12.50
Purchase #6	$140.79	11.108%	$156.429	$156.43	$156.45	$156.40
Purchase #7	$131.74	6.632%	$140.477	$140.48	$140.50	$140.50
7 purchase totals =	$903.72		$994.2725	$994.28	$994.30	$994.30