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	$44.31	3.720%	$45.9583	$45.96	$45.95	$46.00
Purchase #2	$215.61	10.441%	$238.1218	$238.12	$238.10	$238.10
Purchase #3	$48.37	10.798%	$53.593	$53.59	$53.60	$53.60
Purchase #4	$105.39	4.263%	$109.8828	$109.88	$109.90	$109.90
Purchase #5	$221.90	5.339%	$233.7472	$233.75	$233.75	$233.70
Purchase #6	$27.28	13.585%	$30.986	$30.99	$31.00	$31.00
Purchase #7	$246.32	6.835%	$263.156	$263.16	$263.15	$263.20
7 purchase totals =	$909.18		$975.4451	$975.45	$975.45	$975.50