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	$119.41	12.569%	$134.4186	$134.42	$134.40	$134.40
Purchase #2	$25.64	8.807%	$27.8981	$27.90	$27.90	$27.90
Purchase #3	$98.81	12.443%	$111.1049	$111.10	$111.10	$111.10
Purchase #4	$45.59	10.353%	$50.3099	$50.31	$50.30	$50.30
Purchase #5	$53.55	6.380%	$56.9665	$56.97	$56.95	$57.00
Purchase #6	$55.26	8.274%	$59.8322	$59.83	$59.85	$59.80
Purchase #7	$239.88	11.199%	$266.7442	$266.74	$266.75	$266.70
7 purchase totals =	$638.14		$707.2744	$707.27	$707.25	$707.20