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	$42.46	9.451%	$46.4729	$46.47	$46.45	$46.50
Purchase #2	$59.96	8.819%	$65.2479	$65.25	$65.25	$65.20
Purchase #3	$112.87	5.807%	$119.4244	$119.42	$119.40	$119.40
Purchase #4	$88.41	6.595%	$94.2406	$94.24	$94.25	$94.20
Purchase #5	$58.56	12.241%	$65.7283	$65.73	$65.75	$65.70
Purchase #6	$188.54	11.707%	$210.6124	$210.61	$210.60	$210.60
Purchase #7	$164.63	9.179%	$179.7414	$179.74	$179.75	$179.70
7 purchase totals =	$715.43		$781.4679	$781.46	$781.45	$781.30