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	$147.96	3.256%	$152.7776	$152.78	$152.80	$152.80
Purchase #2	$101.79	5.722%	$107.6144	$107.61	$107.60	$107.60
Purchase #3	$94.91	12.302%	$106.5858	$106.59	$106.60	$106.60
Purchase #4	$202.41	3.240%	$208.9681	$208.97	$208.95	$209.00
Purchase #5	$104.95	4.117%	$109.2708	$109.27	$109.25	$109.30
Purchase #6	$79.40	7.189%	$85.1081	$85.11	$85.10	$85.10
Purchase #7	$68.36	4.278%	$71.2844	$71.28	$71.30	$71.30
7 purchase totals =	$799.78		$841.6092	$841.61	$841.60	$841.70