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	$194.85	5.605%	$205.7713	$205.77	$205.75	$205.80
Purchase #2	$24.87	11.185%	$27.6517	$27.65	$27.65	$27.70
Purchase #3	$179.72	5.529%	$189.6567	$189.66	$189.65	$189.70
Purchase #4	$93.69	9.402%	$102.4987	$102.50	$102.50	$102.50
Purchase #5	$102.71	8.515%	$111.4558	$111.46	$111.45	$111.50
Purchase #6	$91.41	8.641%	$99.3087	$99.31	$99.30	$99.30
Purchase #7	$162.27	6.827%	$173.3482	$173.35	$173.35	$173.30
7 purchase totals =	$849.52		$909.6911	$909.70	$909.65	$909.80