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	$14.59	5.325%	$15.3669	$15.37	$15.35	$15.40
Purchase #2	$20.86	13.755%	$23.7293	$23.73	$23.75	$23.70
Purchase #3	$79.97	7.410%	$85.8958	$85.90	$85.90	$85.90
Purchase #4	$196.44	7.553%	$211.2771	$211.28	$211.30	$211.30
Purchase #5	$83.89	7.199%	$89.9292	$89.93	$89.95	$89.90
Purchase #6	$6.40	12.874%	$7.2239	$7.22	$7.20	$7.20
Purchase #7	$53.38	7.784%	$57.5351	$57.54	$57.55	$57.50
7 purchase totals =	$455.53		$490.9573	$490.97	$491.00	$490.90