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	$184.76	5.697%	$195.2858	$195.29	$195.30	$195.30
Purchase #2	$188.30	12.815%	$212.4306	$212.43	$212.45	$212.40
Purchase #3	$142.37	4.537%	$148.8293	$148.83	$148.85	$148.80
Purchase #4	$28.96	11.663%	$32.3376	$32.34	$32.35	$32.30
Purchase #5	$105.29	6.787%	$112.436	$112.44	$112.45	$112.40
Purchase #6	$94.54	10.414%	$104.3854	$104.39	$104.40	$104.40
Purchase #7	$171.61	8.376%	$185.9841	$185.98	$186.00	$186.00
7 purchase totals =	$915.83		$991.6888	$991.70	$991.80	$991.60