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	$183.76	13.734%	$208.9976	$209.00	$209.00	$209.00
Purchase #2	$55.90	3.106%	$57.6363	$57.64	$57.65	$57.60
Purchase #3	$184.81	6.412%	$196.66	$196.66	$196.65	$196.70
Purchase #4	$80.66	5.846%	$85.3754	$85.38	$85.40	$85.40
Purchase #5	$156.55	5.867%	$165.7348	$165.73	$165.75	$165.70
Purchase #6	$238.91	8.156%	$258.3955	$258.40	$258.40	$258.40
Purchase #7	$129.27	6.492%	$137.6622	$137.66	$137.65	$137.70
7 purchase totals =	$1,029.86		$1,110.4618	$1,110.47	$1,110.50	$1,110.50