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	$154.26	8.154%	$166.8384	$166.84	$166.85	$166.80
Purchase #2	$98.76	6.448%	$105.128	$105.13	$105.15	$105.10
Purchase #3	$191.26	11.575%	$213.3983	$213.40	$213.40	$213.40
Purchase #4	$91.50	8.432%	$99.2153	$99.22	$99.20	$99.20
Purchase #5	$134.78	13.697%	$153.2408	$153.24	$153.25	$153.20
Purchase #6	$126.49	3.736%	$131.2157	$131.22	$131.20	$131.20
Purchase #7	$202.92	6.631%	$216.3756	$216.38	$216.40	$216.40
7 purchase totals =	$999.97		$1,085.4121	$1,085.43	$1,085.45	$1,085.30