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	$170.88	13.837%	$194.5247	$194.52	$194.50	$194.50
Purchase #2	$99.83	5.588%	$105.4085	$105.41	$105.40	$105.40
Purchase #3	$85.90	5.157%	$90.3299	$90.33	$90.35	$90.30
Purchase #4	$222.66	6.447%	$237.0149	$237.01	$237.00	$237.00
Purchase #5	$69.92	13.433%	$79.3124	$79.31	$79.30	$79.30
Purchase #6	$147.65	13.605%	$167.7378	$167.74	$167.75	$167.70
Purchase #7	$111.27	13.530%	$126.3248	$126.32	$126.30	$126.30
7 purchase totals =	$908.11		$1,000.6530	$1,000.64	$1,000.60	$1,000.50