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	$186.56	11.243%	$207.5349	$207.53	$207.55	$207.50
Purchase #2	$147.69	6.854%	$157.8127	$157.81	$157.80	$157.80
Purchase #3	$110.66	5.635%	$116.8957	$116.90	$116.90	$116.90
Purchase #4	$53.73	6.825%	$57.3971	$57.40	$57.40	$57.40
Purchase #5	$135.38	12.390%	$152.1536	$152.15	$152.15	$152.20
Purchase #6	$185.60	4.553%	$194.0504	$194.05	$194.05	$194.10
Purchase #7	$123.97	6.390%	$131.8917	$131.89	$131.90	$131.90
7 purchase totals =	$943.59		$1,017.7361	$1,017.73	$1,017.75	$1,017.80