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	$156.47	8.256%	$169.3882	$169.39	$169.40	$169.40
Purchase #2	$61.92	10.846%	$68.6358	$68.64	$68.65	$68.60
Purchase #3	$238.41	3.550%	$246.8736	$246.87	$246.85	$246.90
Purchase #4	$145.58	13.695%	$165.5172	$165.52	$165.50	$165.50
Purchase #5	$58.49	6.793%	$62.4632	$62.46	$62.45	$62.50
Purchase #6	$193.27	9.555%	$211.7369	$211.74	$211.75	$211.70
Purchase #7	$215.48	4.828%	$225.8834	$225.88	$225.90	$225.90
7 purchase totals =	$1,069.62		$1,150.4983	$1,150.50	$1,150.50	$1,150.50