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	$126.88	3.452%	$131.2599	$131.26	$131.25	$131.30
Purchase #2	$35.47	8.407%	$38.452	$38.45	$38.45	$38.50
Purchase #3	$114.65	9.845%	$125.9373	$125.94	$125.95	$125.90
Purchase #4	$92.76	9.805%	$101.8551	$101.86	$101.85	$101.90
Purchase #5	$81.51	5.254%	$85.7925	$85.79	$85.80	$85.80
Purchase #6	$90.44	6.767%	$96.5601	$96.56	$96.55	$96.60
Purchase #7	$152.61	12.301%	$171.3826	$171.38	$171.40	$171.40
7 purchase totals =	$694.32		$751.2395	$751.24	$751.25	$751.40