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	$86.25	11.698%	$96.3395	$96.34	$96.35	$96.30
Purchase #2	$153.74	6.848%	$164.2681	$164.27	$164.25	$164.30
Purchase #3	$175.73	5.582%	$185.5392	$185.54	$185.55	$185.50
Purchase #4	$154.96	9.669%	$169.9431	$169.94	$169.95	$169.90
Purchase #5	$68.65	12.474%	$77.2134	$77.21	$77.20	$77.20
Purchase #6	$105.33	6.259%	$111.9226	$111.92	$111.90	$111.90
Purchase #7	$181.86	7.382%	$195.2849	$195.28	$195.30	$195.30
7 purchase totals =	$926.52		$1,000.5108	$1,000.50	$1,000.50	$1,000.40