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	$64.92	6.367%	$69.0535	$69.05	$69.05	$69.10
Purchase #2	$55.78	6.470%	$59.389	$59.39	$59.40	$59.40
Purchase #3	$205.94	5.783%	$217.8495	$217.85	$217.85	$217.80
Purchase #4	$164.59	4.300%	$171.6674	$171.67	$171.65	$171.70
Purchase #5	$53.75	13.692%	$61.1095	$61.11	$61.10	$61.10
Purchase #6	$112.66	12.844%	$127.1301	$127.13	$127.15	$127.10
Purchase #7	$213.63	9.138%	$233.1515	$233.15	$233.15	$233.20
7 purchase totals =	$871.27		$939.3505	$939.35	$939.35	$939.40