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	$175.41	8.331%	$190.0234	$190.02	$190.00	$190.00
Purchase #2	$125.43	4.658%	$131.2725	$131.27	$131.25	$131.30
Purchase #3	$180.61	5.472%	$190.493	$190.49	$190.50	$190.50
Purchase #4	$55.30	6.268%	$58.7662	$58.77	$58.75	$58.80
Purchase #5	$242.72	10.552%	$268.3318	$268.33	$268.35	$268.30
Purchase #6	$23.87	5.441%	$25.1688	$25.17	$25.15	$25.20
Purchase #7	$225.77	8.725%	$245.4684	$245.47	$245.45	$245.50
7 purchase totals =	$1,029.11		$1,109.5241	$1,109.52	$1,109.45	$1,109.60