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	$188.63	12.355%	$211.9352	$211.94	$211.95	$211.90
Purchase #2	$194.51	5.603%	$205.4084	$205.41	$205.40	$205.40
Purchase #3	$190.48	13.109%	$215.45	$215.45	$215.45	$215.50
Purchase #4	$164.33	6.234%	$174.5743	$174.57	$174.55	$174.60
Purchase #5	$80.88	13.621%	$91.8967	$91.90	$91.90	$91.90
Purchase #6	$204.99	5.504%	$216.2726	$216.27	$216.25	$216.30
Purchase #7	$99.45	5.685%	$105.1037	$105.10	$105.10	$105.10
7 purchase totals =	$1,123.27		$1,220.6409	$1,220.64	$1,220.60	$1,220.70