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	$174.77	13.521%	$198.4007	$198.40	$198.40	$198.40
Purchase #2	$70.72	11.574%	$78.9051	$78.91	$78.90	$78.90
Purchase #3	$57.56	7.836%	$62.0704	$62.07	$62.05	$62.10
Purchase #4	$168.65	8.805%	$183.4996	$183.50	$183.50	$183.50
Purchase #5	$47.56	11.709%	$53.1288	$53.13	$53.15	$53.10
Purchase #6	$74.36	6.310%	$79.0521	$79.05	$79.05	$79.10
Purchase #7	$213.80	8.271%	$231.4834	$231.48	$231.50	$231.50
7 purchase totals =	$807.42		$886.5401	$886.54	$886.55	$886.60