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	$193.27	10.347%	$213.2676	$213.27	$213.25	$213.30
Purchase #2	$103.77	5.498%	$109.4753	$109.48	$109.50	$109.50
Purchase #3	$80.26	11.379%	$89.3928	$89.39	$89.40	$89.40
Purchase #4	$98.25	11.495%	$109.5438	$109.54	$109.55	$109.50
Purchase #5	$80.32	13.343%	$91.0371	$91.04	$91.05	$91.00
Purchase #6	$233.80	10.180%	$257.6008	$257.60	$257.60	$257.60
Purchase #7	$210.28	6.133%	$223.1765	$223.18	$223.20	$223.20
7 purchase totals =	$999.95		$1,093.4939	$1,093.50	$1,093.55	$1,093.50