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	$197.74	13.236%	$223.9129	$223.91	$223.90	$223.90
Purchase #2	$168.89	5.430%	$178.0607	$178.06	$178.05	$178.10
Purchase #3	$138.71	10.691%	$153.5395	$153.54	$153.55	$153.50
Purchase #4	$216.45	7.806%	$233.3461	$233.35	$233.35	$233.30
Purchase #5	$51.37	12.674%	$57.8806	$57.88	$57.90	$57.90
Purchase #6	$239.31	12.184%	$268.4675	$268.47	$268.45	$268.50
Purchase #7	$233.27	13.109%	$263.8494	$263.85	$263.85	$263.80
7 purchase totals =	$1,245.74		$1,379.0567	$1,379.06	$1,379.05	$1,379.00