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	$56.27	6.424%	$59.8848	$59.88	$59.90	$59.90
Purchase #2	$58.37	6.513%	$62.1716	$62.17	$62.15	$62.20
Purchase #3	$45.97	9.667%	$50.4139	$50.41	$50.40	$50.40
Purchase #4	$21.56	3.353%	$22.2829	$22.28	$22.30	$22.30
Purchase #5	$179.74	10.198%	$198.0699	$198.07	$198.05	$198.10
Purchase #6	$86.50	10.413%	$95.5072	$95.51	$95.50	$95.50
Purchase #7	$230.48	10.732%	$255.2151	$255.22	$255.20	$255.20
7 purchase totals =	$678.89		$743.5454	$743.54	$743.50	$743.60