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	$103.90	6.653%	$110.8125	$110.81	$110.80	$110.80
Purchase #2	$28.70	8.688%	$31.1935	$31.19	$31.20	$31.20
Purchase #3	$106.71	11.254%	$118.7191	$118.72	$118.70	$118.70
Purchase #4	$90.37	6.859%	$96.5685	$96.57	$96.55	$96.60
Purchase #5	$33.79	11.694%	$37.7414	$37.74	$37.75	$37.70
Purchase #6	$240.89	6.713%	$257.0609	$257.06	$257.05	$257.10
Purchase #7	$82.89	4.158%	$86.3366	$86.34	$86.35	$86.30
7 purchase totals =	$687.25		$738.4325	$738.43	$738.40	$738.40