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	$109.93	4.137%	$114.4778	$114.48	$114.50	$114.50
Purchase #2	$149.26	5.817%	$157.9425	$157.94	$157.95	$157.90
Purchase #3	$166.33	13.268%	$188.3987	$188.40	$188.40	$188.40
Purchase #4	$109.94	13.874%	$125.1931	$125.19	$125.20	$125.20
Purchase #5	$96.61	3.391%	$99.886	$99.89	$99.90	$99.90
Purchase #6	$168.89	13.847%	$192.2762	$192.28	$192.30	$192.30
Purchase #7	$202.29	12.363%	$227.2991	$227.30	$227.30	$227.30
7 purchase totals =	$1,003.25		$1,105.4734	$1,105.48	$1,105.55	$1,105.50