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	$148.68	10.466%	$164.2408	$164.24	$164.25	$164.20
Purchase #2	$221.66	3.247%	$228.8573	$228.86	$228.85	$228.90
Purchase #3	$222.83	3.627%	$230.912	$230.91	$230.90	$230.90
Purchase #4	$75.89	7.280%	$81.4148	$81.41	$81.40	$81.40
Purchase #5	$82.37	8.397%	$89.2866	$89.29	$89.30	$89.30
Purchase #6	$99.94	11.414%	$111.3472	$111.35	$111.35	$111.30
Purchase #7	$104.62	10.178%	$115.2682	$115.27	$115.25	$115.30
7 purchase totals =	$955.99		$1,021.3269	$1,021.33	$1,021.30	$1,021.30