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	$101.53	3.496%	$105.0795	$105.08	$105.10	$105.10
Purchase #2	$149.44	9.860%	$164.1748	$164.17	$164.15	$164.20
Purchase #3	$60.88	7.219%	$65.2749	$65.27	$65.25	$65.30
Purchase #4	$189.42	9.453%	$207.3259	$207.33	$207.35	$207.30
Purchase #5	$118.29	12.171%	$132.6871	$132.69	$132.70	$132.70
Purchase #6	$109.25	4.748%	$114.4372	$114.44	$114.45	$114.40
Purchase #7	$238.72	6.200%	$253.5206	$253.52	$253.50	$253.50
7 purchase totals =	$967.53		$1,042.5000	$1,042.50	$1,042.50	$1,042.50