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	$87.87	13.484%	$99.7184	$99.72	$99.70	$99.70
Purchase #2	$190.41	3.386%	$196.8573	$196.86	$196.85	$196.90
Purchase #3	$64.52	11.610%	$72.0108	$72.01	$72.00	$72.00
Purchase #4	$22.60	7.363%	$24.264	$24.26	$24.25	$24.30
Purchase #5	$189.34	11.279%	$210.6957	$210.70	$210.70	$210.70
Purchase #6	$227.86	9.862%	$250.3316	$250.33	$250.35	$250.30
Purchase #7	$203.42	7.293%	$218.2554	$218.26	$218.25	$218.30
7 purchase totals =	$986.02		$1,072.1332	$1,072.14	$1,072.10	$1,072.20