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	$55.26	10.566%	$61.0988	$61.10	$61.10	$61.10
Purchase #2	$156.89	7.278%	$168.3085	$168.31	$168.30	$168.30
Purchase #3	$141.33	9.227%	$154.3705	$154.37	$154.35	$154.40
Purchase #4	$64.57	12.515%	$72.6509	$72.65	$72.65	$72.70
Purchase #5	$138.33	5.309%	$145.6739	$145.67	$145.65	$145.70
Purchase #6	$33.88	5.179%	$35.6346	$35.63	$35.65	$35.60
Purchase #7	$103.40	5.843%	$109.4417	$109.44	$109.45	$109.40
7 purchase totals =	$693.66		$747.1789	$747.17	$747.15	$747.20