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	$206.73	11.510%	$230.5246	$230.52	$230.50	$230.50
Purchase #2	$99.38	13.181%	$112.4793	$112.48	$112.50	$112.50
Purchase #3	$83.33	3.539%	$86.279	$86.28	$86.30	$86.30
Purchase #4	$77.68	9.304%	$84.9073	$84.91	$84.90	$84.90
Purchase #5	$138.56	13.139%	$156.7654	$156.77	$156.75	$156.80
Purchase #6	$232.96	9.629%	$255.3917	$255.39	$255.40	$255.40
Purchase #7	$180.37	7.811%	$194.4587	$194.46	$194.45	$194.50
7 purchase totals =	$1,019.01		$1,120.8060	$1,120.81	$1,120.80	$1,120.90