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	$168.40	10.476%	$186.0416	$186.04	$186.05	$186.00
Purchase #2	$97.70	5.532%	$103.1048	$103.10	$103.10	$103.10
Purchase #3	$237.90	6.370%	$253.0542	$253.05	$253.05	$253.10
Purchase #4	$158.94	12.551%	$178.8886	$178.89	$178.90	$178.90
Purchase #5	$53.42	7.228%	$57.2812	$57.28	$57.30	$57.30
Purchase #6	$79.54	12.511%	$89.4912	$89.49	$89.50	$89.50
Purchase #7	$108.65	5.374%	$114.4889	$114.49	$114.50	$114.50
7 purchase totals =	$904.55		$982.3505	$982.34	$982.40	$982.40