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	$246.65	9.147%	$269.2111	$269.21	$269.20	$269.20
Purchase #2	$240.73	5.696%	$254.442	$254.44	$254.45	$254.40
Purchase #3	$63.26	3.252%	$65.3172	$65.32	$65.30	$65.30
Purchase #4	$160.75	12.166%	$180.3068	$180.31	$180.30	$180.30
Purchase #5	$169.83	9.235%	$185.5138	$185.51	$185.50	$185.50
Purchase #6	$91.67	10.512%	$101.3064	$101.31	$101.30	$101.30
Purchase #7	$186.27	13.523%	$211.4593	$211.46	$211.45	$211.50
7 purchase totals =	$1,159.16		$1,267.5566	$1,267.56	$1,267.50	$1,267.50