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	$88.56	3.123%	$91.3257	$91.33	$91.35	$91.30
Purchase #2	$117.60	5.321%	$123.8575	$123.86	$123.85	$123.90
Purchase #3	$234.76	10.273%	$258.8769	$258.88	$258.90	$258.90
Purchase #4	$128.27	6.263%	$136.3036	$136.30	$136.30	$136.30
Purchase #5	$60.61	8.276%	$65.6261	$65.63	$65.65	$65.60
Purchase #6	$70.95	11.171%	$78.8758	$78.88	$78.90	$78.90
Purchase #7	$238.46	13.849%	$271.4843	$271.48	$271.50	$271.50
7 purchase totals =	$939.21		$1,026.3499	$1,026.36	$1,026.45	$1,026.40