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	$101.85	9.319%	$111.3414	$111.34	$111.35	$111.30
Purchase #2	$79.58	7.229%	$85.3328	$85.33	$85.35	$85.30
Purchase #3	$14.35	13.871%	$16.3405	$16.34	$16.35	$16.30
Purchase #4	$178.51	3.851%	$185.3844	$185.38	$185.40	$185.40
Purchase #5	$221.89	12.415%	$249.4376	$249.44	$249.45	$249.40
Purchase #6	$100.49	10.840%	$111.3831	$111.38	$111.40	$111.40
Purchase #7	$157.79	11.549%	$176.0132	$176.01	$176.00	$176.00
7 purchase totals =	$854.46		$935.2330	$935.22	$935.30	$935.10