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	$236.84	3.443%	$244.9944	$244.99	$245.00	$245.00
Purchase #2	$166.33	3.581%	$172.2863	$172.29	$172.30	$172.30
Purchase #3	$78.97	4.354%	$82.4084	$82.41	$82.40	$82.40
Purchase #4	$217.42	13.750%	$247.3153	$247.32	$247.30	$247.30
Purchase #5	$89.41	6.567%	$95.2816	$95.28	$95.30	$95.30
Purchase #6	$131.47	13.360%	$149.0344	$149.03	$149.05	$149.00
Purchase #7	$24.86	9.539%	$27.2314	$27.23	$27.25	$27.20
7 purchase totals =	$945.30		$1,018.5518	$1,018.55	$1,018.60	$1,018.50