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	$82.53	5.595%	$87.1476	$87.15	$87.15	$87.10
Purchase #2	$103.31	11.510%	$115.201	$115.20	$115.20	$115.20
Purchase #3	$214.48	4.220%	$223.5311	$223.53	$223.55	$223.50
Purchase #4	$154.39	9.125%	$168.4781	$168.48	$168.50	$168.50
Purchase #5	$115.39	6.710%	$123.1327	$123.13	$123.15	$123.10
Purchase #6	$109.42	13.200%	$123.8634	$123.86	$123.85	$123.90
Purchase #7	$244.88	9.390%	$267.8742	$267.87	$267.85	$267.90
7 purchase totals =	$1,024.40		$1,109.2281	$1,109.22	$1,109.25	$1,109.20