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	$151.78	5.237%	$159.7287	$159.73	$159.75	$159.70
Purchase #2	$49.72	7.147%	$53.2735	$53.27	$53.25	$53.30
Purchase #3	$100.29	11.857%	$112.1814	$112.18	$112.20	$112.20
Purchase #4	$229.32	4.117%	$238.7611	$238.76	$238.75	$238.80
Purchase #5	$59.40	5.502%	$62.6682	$62.67	$62.65	$62.70
Purchase #6	$212.97	11.380%	$237.206	$237.21	$237.20	$237.20
Purchase #7	$145.34	3.654%	$150.6507	$150.65	$150.65	$150.70
7 purchase totals =	$948.82		$1,014.4696	$1,014.47	$1,014.45	$1,014.60