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	$215.53	5.434%	$227.2419	$227.24	$227.25	$227.20
Purchase #2	$120.69	7.157%	$129.3278	$129.33	$129.35	$129.30
Purchase #3	$74.92	6.674%	$79.9202	$79.92	$79.90	$79.90
Purchase #4	$240.72	7.542%	$258.8751	$258.88	$258.90	$258.90
Purchase #5	$190.31	9.532%	$208.4503	$208.45	$208.45	$208.50
Purchase #6	$79.71	12.819%	$89.928	$89.93	$89.95	$89.90
Purchase #7	$62.54	6.517%	$66.6157	$66.62	$66.60	$66.60
7 purchase totals =	$984.42		$1,060.3590	$1,060.37	$1,060.40	$1,060.30