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	$189.96	5.742%	$200.8675	$200.87	$200.85	$200.90
Purchase #2	$130.96	12.743%	$147.6482	$147.65	$147.65	$147.60
Purchase #3	$66.96	6.454%	$71.2816	$71.28	$71.30	$71.30
Purchase #4	$167.36	5.706%	$176.9096	$176.91	$176.90	$176.90
Purchase #5	$198.83	5.309%	$209.3859	$209.39	$209.40	$209.40
Purchase #6	$67.41	8.155%	$72.9073	$72.91	$72.90	$72.90
Purchase #7	$155.64	8.163%	$168.3449	$168.34	$168.35	$168.30
7 purchase totals =	$977.12		$1,047.3450	$1,047.35	$1,047.35	$1,047.30