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	$106.40	3.787%	$110.4294	$110.43	$110.45	$110.40
Purchase #2	$196.61	4.332%	$205.1271	$205.13	$205.15	$205.10
Purchase #3	$20.40	3.429%	$21.0995	$21.10	$21.10	$21.10
Purchase #4	$104.31	6.535%	$111.1267	$111.13	$111.15	$111.10
Purchase #5	$209.80	6.339%	$223.0992	$223.10	$223.10	$223.10
Purchase #6	$209.72	8.432%	$227.4036	$227.40	$227.40	$227.40
Purchase #7	$82.59	3.589%	$85.5542	$85.55	$85.55	$85.60
7 purchase totals =	$929.83		$983.8397	$983.84	$983.90	$983.80