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	$23.45	3.690%	$24.3153	$24.32	$24.30	$24.30
Purchase #2	$237.46	9.209%	$259.3277	$259.33	$259.35	$259.30
Purchase #3	$98.32	4.363%	$102.6097	$102.61	$102.60	$102.60
Purchase #4	$106.64	8.321%	$115.5135	$115.51	$115.50	$115.50
Purchase #5	$175.62	11.759%	$196.2712	$196.27	$196.25	$196.30
Purchase #6	$242.60	3.299%	$250.6034	$250.60	$250.60	$250.60
Purchase #7	$192.31	11.365%	$214.166	$214.17	$214.15	$214.20
7 purchase totals =	$1,076.40		$1,162.8068	$1,162.81	$1,162.75	$1,162.80