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	$120.44	5.380%	$126.9197	$126.92	$126.90	$126.90
Purchase #2	$81.68	11.790%	$91.3101	$91.31	$91.30	$91.30
Purchase #3	$100.60	7.521%	$108.1661	$108.17	$108.15	$108.20
Purchase #4	$162.77	5.504%	$171.7289	$171.73	$171.75	$171.70
Purchase #5	$221.98	6.672%	$236.7905	$236.79	$236.80	$236.80
Purchase #6	$79.29	12.773%	$89.4177	$89.42	$89.40	$89.40
Purchase #7	$237.88	5.564%	$251.1156	$251.12	$251.10	$251.10
7 purchase totals =	$1,004.64		$1,075.4486	$1,075.46	$1,075.40	$1,075.40